You evict them if they are not following the terms of their lease/rental agreement.Find out what the caps are on rent increases (if there are any). 

I don’t know how partnerships work but I understand how wanting a construction worker as your partner can benefit you. 

Immediately, have them sign a month-to-month lease to formalize your relationship and set basic terms.

Need a new roof in a 3-5 years, you probably want to be pretty liquid (year long CD, Money Market, maybe very short term bond fund etc) for those funds.On a condo board 15 years ago, I  was once able to get us into some nice CD's a decade ago that laddered with the useful life of components.

I thought about starting out with 1 single family residence for long term or midterm rental.

Make sure it explicitly explains the process for termination if you are unhappy with their services, especially if they violate the terms of your agreement.3.

On a short term hard money loan yes. 65% CLTV max 

Quote from @Matthew (Mateo) McDaniel: A hard money lender is typically used for short-term loans.

If I were to do so, I'd definitely look for small multi-family as opposed to SFRs, unless you're wanting to create a short-term rental(STR). 

Short term bridge loan, they require much less down payment (10% or less) after stabilizing the units you can refinance with a better loan option.2.