Whether you are investing for Cash flow, appreciation, looking for value add, or just tax benefits.I first build out my buy box, which the more narrow it is, the better (multi family, 3 units, in XYZ zip code, at this price point per sqft, build after XYZ year......). 

Here is why there are no responses to your question: it's tricky.Prior to the 2018 tax reform, there was a deduction for personal moving expenses.

I was thinking that the cleaning fee could simply be covered by whatever the host is currently charging their guests, and the maintenance fee could be a set monthly amount to cover basic needs such as pool cleaning/maintenance, lawn care, pool deck cleaning, and minor touchups.What do you all think about this?

You may pay $10,000 in interest but you only get back $2,000 back in tax savings. $2,000 is just a random number, the exact number depends on your overall tax situation.Building an ADU if you plan to rent it is business interest, not personal interest.

Excellent deal for the minority partners (zero cash contribution) but a low ROI even accounting for tax savings of $24k/yr on a $500k cash investment.

What are property taxes like there?  

Cons: Loses all other upside (levered returns, tax benefits, appreciation)What do y’all think I should do?

Downside is when it comes time to sell, I would be hit with depreciation recapture tax. 

Are flat-fee MLS sites or otherwise free listing sites like Craigslist the only options?

They have some significant fees and they take control of the asset but it might be worth your time.