I’m just doing a BRRRR on tri plex, had to pay cash for the building and rehab.Then when it’s appraisal ready should get 70% loan to ARV Or all the cost, whichever is lower.

no absolutely not but at the same time I'm going to be cash flow positive based on conservative estimates and only have about ~10k into the deal.Here in NJ, the higher HOA fees are offset by the lower taxes on the condo. 

If he offers to charge you a lower interest rate, accept it graciously.You are only paying him interest on the money borrowed.

One consideration is if it's up to 4 units, I could refinance later on with a conventional loan to get a lower interest rate, so all things being equal I'll hunt for that. 

Hopefully @Dave Foster will chime in if I’m wrong but my understanding is you’ll be taxed on cash you keep or any lower balance mortgage you obtain.

I would not lower my rent for current tenants.2.  

IMO if you chose #1 now you can always choose options #2 or #4 six months(maybe a year) down the road, pull all your 60K back out plus what ever appreciation you have(if any) and move forward. to me in option #3 you said paying interest bothers you and option 1 solves that problem, gives you practice with a new tenant so if they don't pay or u have problems you don't have 2 bills( your old mortgage and your new mortgage) to manage along with the stress(of kicking out your friend and finding a new tenant) just the one mortgage that your fiance already has within his budget(because your 60K didnt' factor into bank financing so you found a home to move to that was within his budget alone(even more safety net) or at least lower mortgage payment and house than if you had 60K to use to buy-down another home. but i digress....Option #1 is less stress , less interest payments,and less of your money with 2 options left over at a later date. like joe said your 60K is safely locked away in the home(minus depreciation) which you can always pull out later on when you are more risk-prove.Still your choice but that my point of view.Good luck!

I guessed on the lower end since I don't assume this park has the most amenities and that much demand.

I was wondering if buying e.g. some land (value approx 25-30% of sold property) would allow me to lower / defer taxes?

I wanted to get input from you on investing in lower income urban neighborhoods.