You can do it yourself mostly with a good real estate attorney drafting up the PSA agreement. 

Maybe rental agreements need to be recorded like a deed? 

If 2 business owners create a contract, are their signatures enough to make it a binding agreement or would getting the contract notarized be a wiser decision?

Maybe you could come to an agreement where you split the profit 70/30 or 60/40.

Whether services are included in the rent or left to the tenant is a matter that depends on your preferences and the terms of the agreement.

Sharing ownership and responsibilities is possible, but it necessitates shared goals and legal agreements.

If so, ask to see the lease agreement because if you happened to purchase the home you're going to acquire that tenant too, which may come with issues.

Later on, the lease and all the addendums need to be looked at in order to evaluate the current state of the agreement.

what does your agreement say?

However, like @Ellis San Jose mentioned above, you will command more $$$ for your property if it is delivered vacant (unless you are getting top market rent for that unit).If you do sell with tenants, be prepared when the prospective buyer requests rent rolls, estoppel certificates, rent history, existing leases, rent due dates, security deposits, and any other written or verbal agreements.