I can just see that this would make certain people feel like they were being trapped into something.

If a tenant contacts us after move-in for a slow drain or blockage during the first month, AND the plumber confirms it is a main blockage (not something at the fixture trap or first drop), we will charge the Owner rather than the tenant.

I found this information about qualifying property:https://www.law.cornell.edu/uscode/text/26/1400Z%E2%80%932(i) In general, The term “qualified opportunity zone business property” means tangible property used in a trade or business of the qualified opportunity fund if— (I) such property was acquired by the qualified opportunity fund by purchase (as defined in section 179(d)(2)) after December 31, 2017,(II) the original use of such property in the qualified opportunity zone commences with the qualified opportunity fund or the qualified opportunity fund substantially improves the property, andI'd like to zero in on this sentence:"The original use of such property in the qualified opportunity zone commences with the qualified opportunity fund"Does this mean one can purchase a new build to qualify?

Similar to you, we'd like to do a 640 sq ft unit (the max allowed in SMC) and are looking at homes with this goal keenly in mind.Are there any hidden traps, things we should be aware of going into this, or things that you wish you had been able to better plan for?

There are many traps in a deal like this for you, that you are not aware of.  

There are plenty of good properties out there, don't fall into the trap of thinking it is either this house or no house.

And even I just fell into the trap of just answering your question rather than trying to figure out something that fit. 

Probably false security, but I feel better knowing carbon monoxide or radon can't be as easily trapped in the houseHow much is the rent?

@Nathan Yarnell the biggest issue with no cash flow is you get stuck in a debt to income ratio trap where you can't buy more property.

@Manolo As I mentioned before an LLC filing as a partnership cannot own an S-Corp.As far as your other comments - rules and traps are in place to avoid abuse.