they have me convinced that my money would be better off managed by them rather than sitting in a target date fund at Fidelity. So I'm considering letting them manage the assets.
LOL they're lying for personal gain.
Read John Bogle's book "Common sense on mutual funds" for why the idea that a "Rain Man" stock picker cannot outperform the market. Yes, maybe by 1% or even 2% in a very lucky year, but they must charge a 1.5% expense ratio to do that, because that stock research isn't free, and Rain Man commands a very high salary. The result is that even if they beat the market a little, they can't beat it by their high expense ratio, and that means they're a net lose compared to an index fund whose mission is to simply mirror the index, and so has a miniscule expense ratio under 0.1% (1/10 of 1%).
I'll have to sign some documents to give them access to my account, but how do I make sure they can't do something like transfer all of my money out of the account?
Because they don't need to transfer the money out to loot the account. Here, the "advisor" (salesman) has a commission-based relationship with a managed mutual fund. The "advisor" tells your Fidelity account to purchase that exact managed fund and flags themselves as the salesman of record. It's a class "A" fund, so you pay a 5% front-end load to get into that fund. Your "advisor" then gets a ~5% sales commission for placing you in that fund (and that's where the front-end load went). And they can repeat as often as they please.
That fund isn't any better than the index funds you were already in, which means just like that, the salesman just looted 5% out of your nest egg into their pocket.
It's even worse, because "front-end loads" as a concept create a false sense of "Lock-In" or "fallacy of sunk costs", which means you're reluctant to bail out of it when it becomes a loser or there's a better investment over there. They could even tank the fund on purpose to loot money out of it. Your "Advisor" is not really shopping for good investments for you, they're after good investments for them.
Corrupt? Self dealing? Are you kidding me, that arrangement is traditional business-as-usual, and doing this is the reason A-class mutual funds exist. This is the norm of how old-school brokers ("financial advisors") operate. Only in the last 30-40 years did discount brokers like Vanguard, Fidelity and Schwab start earnestly attacking the old school and giving people a genuine alternative that didn't involve fleecing. Bogle's book I mentioned was the clarion call for this revolution, and Bogle started Vanguard to do exactly this.
And you may have noticed that the "financial adviser" doesn't charge much. Now you know how they are compensated. Again, this is the industry norm, so no one is going to call it a swindle. (Other than populists like Bogle).
By the way, I hold ETFs, and I can pop out of an index fund ETF at 11:15 and be in a different index fund at 11:17. You really shouldn't day-trade ETFs :), but you see where I have absolutely no "lock-in" or loads.
All of my financial dealings in the past have been with big-name institutions, which made me feel comfortable and that I could trust them.
You need to use your own judgment regarding trust, but being a big famous company doesn't help. They are some of the worst for this, because this is the traditional practice in stock-brokering.
Now, if you say "No A-class funds", they are way ahead of you. They have increasingly complex financial products - derivatives, insurances, annuities - that are brilliantly crafted/structured to conceal hidden fees and costs. The products are complex on purpose to make it impossibly difficult for non-investment-bankers to understand and track what is going on inside them.
These guys do this for a living, and it's very much a confidence game - they are gaming your confidence.
Note that there is nothing about this advisor or their behavior that has made me suspect anything about them. If it's a scam, they've done a great job.
Of course. That emotion you're feeling of comfort and readiness, their entire job is to create that feeling. They're much more a "people handler" than they are a "technical investment expert". So yeah, you're probably dealing with a highly competent "people handler".
Now if you want good advice, there are "Fee-ONLY" advisers who are actual financial advisors and do not have any of the usual corruptions, commissions or other financial stake in the recommendations they make to you. These guys generally think Bogle. They are harder to find, since they do not widely advertise.