My latest and nicest building is in the bottom 2 towns in my area in terms of services and overall location.

Make sure it explicitly explains the process for termination if you are unhappy with their services, especially if they violate the terms of your agreement.3.

I have a property in Denver that does great with mid-term so I toyed with trying mid-term with a townhome I bought in Kissimmee—not too far from your clients' place.

Now, we do live in a small town, touristy area that does lack in nicer/unique short-term rentals. 

Did they give any additional details?

In terms of getting into apartment complexes and large transactions - it's much easier than you think.Real estate is filled with opportunities to deploy capital, but in the same time is filled with fast-talking snake oil men that will happily take your money towards a "fund" so you own a portion of a large portfolio... only to find out the fund's performance is below par, your money is locked out, and the only person making money is the fund manager from the management fee they've locked you into. 

A signed agreement should contain deposit terms.

Regarding payment terms, the seller wants 10% at the reservation of asset (this month), 10% in a couple of month, and the balance at the signing of the deed of sale in December.

In addition to being a long-term real estate investor I have been a commercial/res appraiser, historic property renovator/contractor, property mgr and more so I don’t mind properties with issues as long as they are fixable and priced accordingly, and my investments are all about the numbers (NOI/Equity).

You can explain that any changes to the lease must be carefully considered, as you want to maintain the original terms that protect your interests.If you decide to allow the change, you could draft an addendum stating that each tenant is responsible for their own rent.