But Brexit has somewhat reduced my appetite to continue building that business!

Any expenses in excess of your rental income from related parties is not deductible. 

I am sure  there is excessive wear and tear.

As Elijah said, if the deals aren't cash flowing in excess of the preferred return on day 1, don't distribute monthly.

I can certainly understand the appetite for lenders to tighten lending requirements - it’s happening across the board.

Full disclosure - My wife and I don't have a real appetite for risk.

So we pay title company > title company pays loan, and if there is any excess, this goes to the seller/original borrower.Assumptions, while they still happen, are much more rare in my experience. 

But the truth is I budget conservatively and would rather have excess reserves than be scrambling to come with cash when expenses come up.  

Even though they are paying for the utilities, it is putting excessive wear on the system and I worry it will fail prematurely, which would be my cost to bear.Does such a product exist?

I like deals that generate 2k or a more, a Month, in excess cash flow after all debt seduce and expenses are paid for.