Then thought, well last year I bought a condo and started house hacking before I knew there was a thing called house hacking and it substantially reduced my cost of living there, maybe buying rentals could actually work. 

But maybe nothing would be saved if registering as a foreign entity is substantial.

You get the rent payment the day you give them the keys.I would take nothing less than the full deposit, if you start taking payments then your renter is learning they can control you, if you do take payment on security deposit, I'd make sure you get a substantial amount and no checks, money order or cashiers check.

Maybe it qualifies, maybe it doesn't.There is sufficient complexity here that a tax professional should be engaged to determine if you have substantial authority or reasonable basis to use the 121 exclusion based on the face value of the facts and the language of the code and regs.I wouldn't take a tax position here based on free advice... 

It looks pretty substantial 

It is my understanding that I will not be subject to self-employment taxes because I don’t think I offer any substantial services...

Now, with that said, if they have the ability to purchase the property and resell it- that's a different story, but most are having people take their property off the market, on a gamble that they can find a buyer, and then take a substantial amount of the sellers equity for it.

I have a substantial cash sum in a money market account from a company sale.

The market you invest in will have a substantial impact on your results.

@Justin Kurpius - I believe you are not conducting a thorough enough analysis of a possible way to lose badly on this investment approach, and are not giving enough weight to perhaps the most probable outcome of this bet:How to lose badly:What happens if the price of gold falls substantially?