He has upgraded my property knowing that I own everything if he was to leave.

And, no, there really isn't a way you can buy it and leave his mortgage in place without a subject-to deal.As long as you are not afraid of being scoffed at, you can tell him, look, I'd normally want to buy this at $100K (I have to resist scoffing at you myself) but I know this is rehabbed and ready to go. 

I would assume many would leave, then I have these trailers.  

Am I better off leaving “the” out of the name? 

We both have come to a point where our 9-5 jobs as a Graphic Designer and Auto Technician are just not satisfying, and we have a hard time leaving our dog home for hours without us.

So, if the person didn't pay or leave, I could evict them as a defacto tenant.

If I leave, do I then need to convert it to a conventional loan?

By screening applications and selecting people with secure jobs, good income, and good credit, you will reduce the risk a ton.I manage 340 rentals and less than 1% of them ever leave owing more than I have on deposit.

This is definitely not a BRRRR that I'd consider.Your purchase, rehab and holding costs put you at full market value.With these numbers you'd be in it for $90k and it's worth $90k.75% LTV refinance you'd get back $67.5k essentially leaving $22.5k + closing costs stuck in the deal.The idea with BRRRR is to force appreciation so you have equity to refinance back out.

You should also have less trouble with vacancy if you buy MFHs, because even if one tenant leaves, there will still be other tenants paying their rent; single-family properties don't have this luxury.At this point, it’s your decision on what type of property to acquire.