To obtain impact worthy return requires a lot of units.  

Property Requirements: Are there any specific requirements for the property being purchased, such as condition, location, or type?

What are typical down payment requirements?

You can househack with FHA or conventional financing - FHA will require 3.5% down and conventional requires 5% down.

I would always specify that is primarily not "solely" based on the property - Credit and liquid reserves are still a significant part of the underwrite Ofcourse credit and technically with commercial DSCR there are no reserves required but yes as minimum as 3 months :) upto 80% cashout with no seasoning too which is wild . 

While this may exempt it from being classified as a rental activity, active participation remains a requirement, necessitating compliance with three tests: spending 500 hours on the property, dedicating at least 100 hours (and more than any other participant), and performing all the necessary work needed.Additionally, long-term viability and consideration of depreciation recapture are important concerns.

If not, I would still recommend going ahead with a professional cleaning company that has experience with mold remediation (make sure they send before and after pictures as well), if you really wanted you could give a small credit to the tenant to make them happy as well but 100% not required. 

I've also had one potential tenant tell me that "an income requirement of 3x the monthly rent basically disqualifies single-income families".

Required agency agreements will be the new norm going forward, not what caused the lawsuits.

HELOCS do exist for rental properties but you are usually capped at 65-70ltv and these will most likely require a full underwrite that takes into consideration taxes, income, dti and all the normal quasi-associated red tape.