Their appraisal appraised $90,000 less compared to mine. 

Aside of things like properly identifying parties, property, competence of the parties, mistake, fraud, meeting of the minds, etc, there are three essential elements required to form a binding contract:Offer - one party offers to sell, lease, or otherwise transfer ownership of an item to a buyer.Acceptance - the other party accepts the first party's offer.

You should definitely shop PMs and understand what comparable units are renting for, their condition, amenities etc.

I'm not saying you shouldn't look at this area, but compare it to at least one other market.

I used comparables through similar sites to what you mentioned and made a list of notes next to them like "similar condition to ours" "small bedrooms" "has a pool" or whatever else was like/unlike our units and then picked in the higher percentile of rents because I knew we would provide more benefits than other units.

This makes more sense for me because it is passive compared to how active my multifamily property was, even with a property manager.

The only other differences I'd see are hurricane windows/door, metal roof, the house designed for the coastal elements, ect. 

If you're serious about investing think about the time sitting on the sideline compared to the opportunities and ROI for properties you could have purchased.

After the unit is empty we do a video walk through with the tenant and can compare it to the video we did on day one.

We can easily cover the mortgage with our W2 income and we anticipate we will cover the mortgage and then some with the STR income (it has a track record of this with current owners and also comparing data from surrounding comps).