@Joseph O'Sullivan
Its a matter of opportunity cost... You realize that if you were in the C fund last year, you'd be up ~27%? Yes, the market goes up and down (and that example is one fantastic year, although we've had a lot of them)... I know this is a real estate forum, but just realize that you'd have missed that AND lost 5% since you have to pay yourself the G fund rate, vs. the G fund paying you.
I'm not anti-real estate, but I don't prefer it when people take extra risks with their retirement. You can still lose money in real estate. Look at any graph youwant, but just realize what really matters is what your "ONE" property is worth.
5yr term isn't bad, but you need to have a solid plan to get that paid back.
brrr is a great strategy, however, its difficult to pull off 100%. We had a long thread about that a while back, before rates shot up. So, it'll be even harder now. Lets face it, a brrr is basically a flip you don't sell. Who really thinks making a profit on a flip isn't risky??
Don't forget that the tsp repayment will be counted against your DTI when looking at conforming loans.
Otherwise, it seems like you understand the risks. Its up to your investing strategy and goals. Depends on how you want to look at it: opportunity cost? diversification? education?
Hope this helps. Happy to chat. Good luck.