I know that buying a house, as opposed to renting, is often a very good financial decision: you have to live somewhere, and paying off a house instead of throwing money away on rent often makes alot of sense. However, what changes if you're planning on moving every few years? The realtor and closing cost fees are often high enough that you'll lose any principal you may have paid off. Are there alternatives to this approach? Is there some type of investment scheme that allows one to avoid paying rent costs while also still moving around?
If I were planning to move every few years, I'd seriously consider renting, rather than purchasing.
And remember - a home isn't an investment, it's a living expense.
Buying is not always better than renting, even if you aren't mobile! That depends on local market conditions.
If you're investing the money reasonably you may do as well as or better than the house-buyer, and your funds will be tremendously more liquid.
If you have a view on housing you can buy a real estate investment trust and use proceeds to pay rent. Downside is, depending on where you live, you'll have to pay tax on dividend income from REITs. So if you invest the same amount in a REIT as in a house you'll effectively loose some money due to the tax. You can also think of it this way: you wouldn't pay tax on the rent that you don't have to pay as a result of owning a house, but you pay tax on rent that other people pay you.
Remember that the rental market and the property market are markets. For any given location and level of quality, if it were a clearly superior choice to buy over rent, then more people would buy, and less would rent, driving prices down for rentals. The value of "owning" as opposed to paying rent and never owning is priced into that, at least at locations and levels of quality where owning is a possibility (and that is nearly always a possibility, even at very low levels of quality).
This is true even disregarding your personal circumstances, unless you're looking in an area that has a lot of people like you (San Francisco, perhaps). Given your personal circumstances, you have strong incentives to be on the renting side, unless there are major pressures on the housing market that cause property to be far cheaper than it should. This was true in 2009-2011, but is mostly not true anymore (though some areas have yet to fully come out of the crash).
I don't know any clever way to do what you're describing. And, in a sense, you can see why there might not be one. A mortgage isn't just a magical way to reduce your housing expenses; it's a tradeoff in which you agree to a long-term commitment in exchange for fixed costs (or at least costs with a prearranged structure) over that long term. If you're unwilling to accept the obligation of paying for and maintaining the property over a long period, you can't really expect to reap the benefits of lowered costs. Part of the reason people say buying is better is because people often do live in the same place for a long time, in which case, if they rent, they might miss out on savings they could have had if they bought instead. If you're not going to live in the same place for a long time, buying may not actually be better for you.