Shouldn't be any extra taxes involved.

I'm soon closing on a multi-family property that has some extra space that's begging to find a better use. 

Your Solo 401k can sell and carry the note.  

These expenses can create a paper loss, which may offset other passive income or carry forward to future years.If you qualify for Real Estate Professional Status (REPS) or actively manage a Short-Term Rental (STR), the losses can be applied against your active W-2 or business income, reducing your overall tax liability.

One of my places had a little extra room next to the kitchen so we made a dedicated coffee area with a coffeepot, a drip setup, a french press and a pod machine.

However, they can carry more risk if vacant and usually offer less cash flow.Multi-family properties provide steady income from multiple tenants and scale your portfolio faster, but they require more upfront capital, stricter financing, and can be harder to manage.If you're new, starting with a single-family home is a simpler way to learn.

New unit: 4-unit multi family in which 3 units (with existing tenants that will carry over from seller) will remain investment; I will move into (currently empty) 4th unit AND USE as primary residence with primary mortgage.

It would be $1.1m, and according to AirDNA it would run -$40k/yr as an STR, and while local rent rates are high it would still run about -$2500k/m.It is such a cool and unique property I hate to let it go and would love to find a creative use for it that could at least carry itself (approx $6k/m+).

I've allowed pets in my STR for five years and haven't had any problems except some extra cleaning a couple times, which was paid for by the guest. 

3) It's been 5+ years since we've seen a S8 tenant lose their voucher for property damages, not paying their portion of the rent or utilities, or other lease violations (letting others move in with them).It's our opinion that #2 & #3 above are caused by overworked caseworkers not having the time to process the extra required paperwork, so they take the path of least resistance.4) S8 needs someone at the federal level to put more of the program online and streamline the process!