Many of them charge an additional fee over 10 feet, and some are scammers just looking to get in your house and try to tell you that you need a whole bunch of other services (that they can provide for an additional fee).  

The buyer seems to be exploring how much of a deal can be had. 

If you have equity in the property you need to deduct a 10% return off the top of the rent as a additional expense otherwise the equity is being wasted.

I work with a lot of different attorneys in the area because I'm a Realtor in addition to being an investor, but John is my attorney.

Are there any other avenues we should explore?  

If you need income now - consider buying outside of an IRA in addition to SD IRA since you will not have access to those funds till retirement.

The property would be a good addition to my portfolio but I am not sure how to accurately estimate the value due to the poor record keeping by the owner. 

I probably should also have mentioned that I renovated my own home, completely, including a second floor addition back in 2005.

In addition, a form should be sent to each tenant requesting a list of payments made to the PM for the last three months, at least for the first year

Obviously I don't consider this a great deal and I have no reason to believe that he will actually pay me the additional $600.