I've actually had an investor give two of the properties back to me after religiously making his payments for 3 years on time but got a set of bad tenants and could not maintain the rentals. 

It has been a very bad and costly experience. 

Make sure the zoning, local building department/regulations, and neighborhood allow you to put a tiny house on your property and rent it out.If that is not possible, using that money for the next property makes sense.In general, I think increasing housing density will help provide more badly needed housing affordably.To Your Success!

If a faucet goes bad and I grab one out of the warehouse who did I bill it to the first time, and how do I change the books to reflect who got it? 

Mostly due to the fact my spouse and I agreed on her to have zero involvment in any sort of RE investing (and its our home) I think once you have a good 6-12 months of reserve cash (operating expenses for your own life saved as a back up incase things go bad) save enough liquidity to get the ball rolling on your first invesment.

spelling out expectations is never a bad thing.So far it has never been an issue. 

A good manager can improve performance for a mediocre investment; a bad manager will kill a good investment.

A full back office. 3 workbooks to use in the 40 hour cI get it just like any non certified or accredited  training.. not saying its bad. but its not a state license so not governed by any state and there is no NMLS registration required..

Just as bad as the posts you see from time to time of the grandchild wanting to work out creative financing to buy their grandparents house below fair market value.  

Anything below is likely in a bad spot.