I have the home owner willing to do owner financing for 6 months to a year with interest while I rehab it then re-fi and pay him off.

I believe if your mother-in-law runs out of money that Medicaid will step in and pay for the nursing care.

Also, the amount of damage was so expensive to repair that he simply could not afford to fix the more damaged units.

They are paying for some repairs now after I've had several issues and a brand new tenant moved out, but I'm still paying a mortgage without any rent coming in during those months. 

You are looking at this through the lense of cash flow, don't forget you are also paying down the mortgage and might see some appreciation, so equity growth might be more than cash flow.

Can I pay property taxes in January that are due now, then deduct them as well as next years that I will (plan to, anyway) pay in December of next year?

But real estate will pay you money today and real estate will pay you even MORE money tomorrow. 

Here is some info: SF STR FAQAssuming the info is up-to-date, it must be your permanent residence (you must live at the property for a minimum 275 days a year), you can rent unhosted a max of 90 nights a year, you need a business license, and you need to pay the city $925 for a STR certificate.

Many voucher holders also work and so sometimes they will have a higher amount to spend than someone who doesn’t work because they can pay up to a % of their net income from the HA’s calculations, often 30-40%.

Our life is complicated and I work a complicated stressful job, but if we’re being honest, I also don’t have time for renters, but I somehow make it work and I personally think it pays off.Mtg: 1800Rent: 2900Owe: 200Rate: 4.5 I thinkSell Price: est. 450-460No other rentals except an in law suite on our current primaryFuture goals: would love to use this properly to buy other properties to get out of the corporate rat race.