I was wondering if anyone would be willing to share a very simple Property Mangement Agreement. 

In terms of appraisal accuracy, 90 percent of appraisals come in above the purchase and sale agreement, which may suggest a bit of confirmation bias on behalf of the appraiser whereby they are justifying the contract price rather than independently arriving at the value.

We will be looking to buy the home some time at the end of the year since we are both building our credit (my wife already has her’s above the minimum for an FHA loan).

Do I still find the ARV of the property if I’m just looking to purchase and assign the contract?

So if you wrote it out in the lease, and the agreement doesn't put either party in a position where they are breaking any laws, your contract may very well be enforceable. 

If you're in a traditional agreement of sale there should be a specific time period for when the inspection needs to occur, how many days you have (buyer) to request repairs, and how long you (seller) has to provide feedback on requests.

They are not on the rental agreement - I don't think they can 'pay rent'. 

Another reason is I do that is it is in some city you regularly travel to for other business-related things.Try to keep your traveling expenses to a minimum. 

A clause or addendum to the purchasing agreement?

Do you have a purchase & sale agreement template?