Tell them when they pay the rent, you need a copy of the utilities bills to ensure they are being paid or as you said you pay and they add it to their rent. 

Additionally, they can know of contractors or be able to offer rough costs for typical improvements.Remember that accurately estimating rehab costs is a skill that improves with experience.

Additionally I tend to get first looks from developers, direct owners, and other brokerages before stuff is listed because they know me and that I screen buyers and make sure they have the ability to purchase and are not flakes and time wasters.  

Hope this additional insight helps you in making your decision. 

@Bill J Fay, I like the idea of asking for current projects or examples of work in addition to references.

In addition, what will happen to the tax write off since both properties are paid off? 

That puts debt against the house.

The accounting aspect is a an additional thought I hadn't heard before.I know some people have used this strategy in an attempt to avoid triggering a re-evaluation of property taxes.  

I believe the future is to hold them and sell them later on contract to allow yourself to have the additional cash flow without the huge gains

The additional time to close will more than pay for itself in the long run!