The ones I've found have the best value were ultimately side-hustles for the founder, and they were making most of their money from their real estate. 

One of my concerns is that lenders won't lend to potential buyers because it is a modular home.

You may not care, but I want to be clear that she is the one in the wrong, not you.

Spring may be better but I was unable to sell a cheap house in October for 5% off of “market value” and only sold a $600k home in January by listing it for $580k and I still only got one offer. ($150k down, 5 year seller financing.) my point being you may get $20-$40k more in a year if you don’t need to sell. 

Business growth - master one market vs. trying to be everywhere. 

And my options are: -One $800k property in CA (25% down), or-Two $400k properties in ID (both at 25% down).If we take the 2015-2020 5-year appreciation (so as not to include the roller coaster and unlikely 5-year market we experienced from 2020-2025) for each state, the CA property would see an average appreciation of 37%.

But of the options you note, the only one that really makes sense to me is the CoC option. 

These all require applicants to submit an acceptable Letter of Explanation addressing each specific issue and occurrence.Rental HistoryBecause a current landlord may say anything to get rid of a bad tenant out of desperation, we also require information for the previous landlord of all applicants…Analyze IncomeMany landlords require a month of paystubs from applicants and just use these to calculate a monthly qualifying income…Employment StabilityUnless an applicant has exceptional credit, we strive to determine their stability of employment…AssetsWe are one of the few management companies that requires a bank statement as part of our application process…Letter Of ExplanationAny time there are credit issues or we discover an inconsistency, we require a written letter of explanation (LOX)…UnderwritingTraditionally, landlords have only looked at the income of applicants…ApprovalOnce an applicant is approved, we require a nonrefundable Holding Fee to make sure they are serious…

House hacking is one of my favorite investment and wealth building strategies.

The barrier to entry in the real estate game is scary to "us" that have not jumped the barrier that programs like this one are very intriguing and attractive.