At the end, the wife found another job and they are paying on time every month, not only that they maintain the house really good which is a big plus.You learn from each tenant that you have but make sure to do a proper due diligence every time that you scan a new one.

I have a unique idea for this space! 

I live in Flanders.I would love to share some ideas with other Belgians.

Based on peoples experiences in MTR in Denver area, is it a good idea to turn a house into MTR, especially of such size?

My only concern with shower doors is that I've found that most tenants don't properly clean it as they are a bit harder to get into the tracks and everything so there may be a bit more mildew/soap scum build-up than what you would see with a curtain. 

Are you working with a Realtor® or a contractor, both can likely solve your problem as the agent will have access to more data and knowledge of how to run comps, the contractor will be able to give you a better idea of repair costs.

Her idea at present is going to be to purchase the house herself (using traditional financing - high interest rate) and make the payment affordable for the family's rent to cover by arranging the sale well below market value and putting up a down payment of 30+ % of her own money, resulting in a PITI of ~1500.

If you can't afford the property with a vacant unit it's probably a bad idea.

Of course, with all things, the answers to all these matters will depend on the circumstances.California tends to have more laws on the books and requirements and restrictions that it can be a good idea to form a CA LLC for out of state property so that you as a CA resident are covered, and to try to have your contracts fall under the purview of CA courts.

Part of Florida's mechanic lien statute:713.06 Liens of persons not in privity; proper payments.—(1) A materialman or laborer, either of whom is not in privity with the owner, or a subcontractor or sub-subcontractor who complies with the provisions of this part and is subject to the limitations thereof, has a lien on the real property improved for any money that is owed to him or her for labor, services, or materials furnished in accordance with his or her contract and with the direct contract and for any unpaid finance charges due under the lienor’s contract.