These factors collectively contribute to a successful sale and maximize the property's value.

1) I always use zillow to list new properties and use there platform to accept zillow applications2) Doorloop for management that includes accounting, repository for documents like leases, collect rents, tenant communications3) Received lease agreement from a lawyer

I am considering other options to see if there are ways I can hire someone to just do showing only and mamage my own rent collection through Zillow app, I also have my own contactors to do maintenance but have been paying monthly fee to my property manager who has done literally nothing, they also never answered my calls.It definitely sounds like you need to reevaluate your relationship with your property manager.

Payment methods, tax collection etc.

He collected first/last/security payments prior to move in date and was never heard from again.

And you avoid things like damaged properties (guest insurance from airbnb or prop manager themselves cover that), evictions, collections, etc.   

They have to collect the data, confirm the data, then publish the data for the public.

And STRs really help because you don't have the large dings that long term rentals have - i.e tenants damaging the property to where you have huge make ready costs (the str insurance covers that), no collections or evictions issues. 

Did you collect and keep an earnest money deposit from that buyer?

Also, focus on 2 years of job/income stability.Class D Properties:Cashflow vs Appreciation: Typically, all cashflow with little, maybe even negative, relative rent & value appreciationVacancy Est: 20%+ should be used to cover nonpayment, evictions & damages.Tenant Pool: majority will have FICO scores under 560 (almost 30% probability of default), little to no good tradelines, lots of collections & chargeoffs, recent evictions.