My work is steady; even if I lost my job it'd be easy to get another. Location has been static for a few years now, but I'm not sure that'll extrapolate to the future; I'm lazy, so I don't want to move, but for a significantly better job opportunity I wouldn't mind.
The general rule of thumb is that you'll come out ahead if you buy a house (with a mortgage) and live there for five years. What you lose in interest, you make up in rent. And living there for five years, you make back your closing costs in equity. If you're there less than five years though, you don't make back the closing costs. You'd have been better off renting.
Historically (up to about twenty years ago), your mortgage payment and rent payment for the same basic property would be about the same. I.e. if your current landlord sold you what you are renting, your mortgage payment would be roughly the same as your rent. Maybe a little lower or a little higher but about the same. More recently, it hasn't been strange to see a divergence in those. Now it is not uncommon for a mortgage payment to be 50% higher than rent on the same property.
This has some consequences. First, your $1000 rent probably won't stretch as far as a $1000 mortgage payment. So you'll be buying something that you'd only pay $650 or $700 rent. Second, if you move and can't sell immediately, you'll get less in rent than you'd pay in mortgage. Rather than contributing to your income, the property will require subsidy just to maintain the mortgage. And in the early years of the mortgage, this means that you're paying all of the principal (equity) and some of the interest.
Buying a duplex makes this worse. You have your side and their side. You can substitute your $1000 rent for half of the mortgage payment. Meanwhile, they are paying $700 in rent. You have to subsidize the mortgage by $300. Plus, you are talking about hiring a property management company to do things like lawn maintenance. There goes another $100 a month. So you are subsidizing the mortgage by $400.
I don't know real estate prices in Utah, but a quick search finds a median house price over $200,000. So it seems unlikely that you are buying new construction with new appliances. More likely you are buying an existing duplex with existing appliances. What happens when they fail? The renter doesn't pay for that. The property management company doesn't pay for that (although they'll likely arrange for it to happen). You pay for it.
Also, it often takes a bit of time to clean up the apartment after one tenant leaves before the new tenant starts paying rent. That's a dead weight loss. If this happens during a local recession, you could be carrying the mortgage on a property with no offsetting rental income for months.
There are some countervailing forces. For example, if house prices in your area are increasing, the rent will increase with them (not necessarily at the same pace). But your mortgage payment stays the same. So eventually the rent may catch up with the mortgage payment. If you wait long enough in a strong enough market, the rent on the other half of the duplex may cover the entire mortgage payment.
If you currently have an urban apartment within walking distance of work and switch to a suburban apartment with a commute, you have a better chance of finding a duplex where the entire mortgage payment is only the $1000 that you pay in rent. Your half of the duplex won't be as nice as your apartment is, and you'll have a half hour or hour long commute every morning (and the same to get home in the evening). But on strictly fiscal terms you'll be doing about as well. Plus you have the income from the other half. So even if your mortgage payment is more than your rent payment, you can still break even if the rent covers it.
Consider a $1400 mortgage and $400 in rent from the other half (after property management fees). So long as nothing goes wrong, you break even. Perhaps the agreement is that your parents take care of things going wrong (broken appliances, troublesome tenants, time between tenants). Or perhaps you drain your emergency fund and adjust your 401(k) payment down to the minimum when that happens. Once your emergency fund is replenished, restore the 401(k).
If you're willing to live in what's essentially a $500 apartment, you can do better this way. Of course, you can also do better by living in a $500 apartment and banking the other $500 that you spend on rent. Plus you now have the expenses of a commute and five hours less free time a week.
You describe yourself as essentially living paycheck to paycheck. You have adequate savings but no building excess. Whatever you get paid, you immediately turn around and spend. Your parents may view you as profligate. Your apartment is nicer than their early apartments were. You go out more often. You're not putting anything aside for later (except retirement).
It didn't use to be at all strange for people to move out of the city because they needed more space. For the same rent they were paying in the city, they could buy a house in the suburbs. Then they'd build up equity. So long as they stayed in roughly the same work location, they didn't need to move until they were ready to upgrade their house.
The duplex plan leads to one of two things. Either you sell the duplex and use the equity to buy a nicer regular house, or you move out of the duplex and rent your half. Now you have a rental property providing income. And if you saved enough for a down payment, you can still buy a regular house.
From your parents' perspective, encouraging you to buy a duplex may be the equivalent of asking you to cut back on spending. Rather than reducing your 401(k) deposits, they may be envisioning you trading in your car for a cheaper one and trading in your nice but expensive apartment for something more reasonable in a cheaper neighborhood. Rather than working with a property management company, you'll be out doing yardwork rather than cavorting with your friends. And maybe the new place would have more space to share when you meet someone--you aren't going to provide many grandkids alone.
If you get a mortgage on a duplex, you are responsible for paying the mortgage. You are responsible even if something happens to the house. For example, if a fire burns it down or a tornado takes it away. Or you just find that the house isn't solid enough to support that party where all of your friends are jumping up and down to the latest pop sensation. So beyond losing whatever you invest in the property, you may also lose what you borrowed.
Now consider what happens if you invest the same amount of money in General Motors as in the house. Let's call that $10,000 and give the house a value of $200,000. With General Motors, even if they go bankrupt tomorrow, you're only out $10,000. With the house, you're out $200,000. Admittedly it's much hard to lose the entire $200,000 value of the house. But even if the house loses $80,000 in value, you are still $70,000 in the hole.
You don't need a disaster for the house to lose $80,000 in value. That's pretty much what happened in the 2006-2010 period. People were losing all of what they invested in houses plus having to declare bankruptcy to get out of the excess debt. Of course, if they had been able to hold on until 2015 markets mostly recovered. But if you lost your job in 2008, they wouldn't let you not make mortgage payments until you got a new one in 2012.
When you declare bankruptcy, you don't just lose the house. You also lose all your emergency savings and may lose some of your belongings.
There are some pretty prosaic disasters too. For example, you and your tenant both go away for a weekend. It rains heavily and your roof starts to leak due to weak maintenance (so not covered by insurance). The house floods, destroying all the electronics and damaging various other things. Bad enough if it's just you, but you're also responsible for the tenant's belongings. They sue you for $20,000 and they move out. So no rent and big expenses. To get the house livable again is going to take $160,000. Plus you have a $190,000 mortgage on a property that is only worth about $40,000. That's at the extreme end.