Have you worked with any quality property managers?

And in any event, because multi-family data is found in less quantity and quality than would be ideal (far from it in your case) an appraisal of such properties will always be weak.Here is my advice for the future - ignore almost everything in the appraisal with exception to two things.

I rented it out several years ago - I can keep it rented, although quality can be an issue at the beach.#3) Land in same place as #2. 

That quality of life has demographers estimating another 1 million people will live in the metro area by 2040.

You need to talk to other investors in the area to get a feel for the quality of the property managers.

For term-based work (construction, renovations, additions, etc.) set completion dates, paid milestones, and if you can afford it, bonuses awarded for completing work ahead of schedule (with specific wording to make sure they complete work up to code, quality, etc.)3.)

Otherwise, vet your contractor based on their quality of work and management skills and live with the results.

Are they over-rehabbing - putting in above-standard quality items that will never generate a proportionate increase in value? 

@Lily Nelson generally if you are priced right and listed on the major rental sites in a city of decent size you shouldn't have a problem, keeping tenants has a lot to do with the quality of the unit but some things are beyond your control, responsible tenants eventually buy homes in most places. 

. $80 a month gets you unlimited but it is throttled back to 3g speeds after 15gb of usage.