In an example like that waiving some late fees to avoid eviction costs, additional nonpayment until eviction, turnover/vacancy costs is well worth considering.

For a low-cost solution, you can create a simple Google form with custom questions and share the link with them.

Your example:1M purchase, sale of $1.4M then a $400K gain is forgetting your rehab and sales costs of approximately $150K, so your real gain is $250K. 

I hired a local handyman by father knew to 'save on repair costs' as opposed to going with one of my usual GC's.

Know the trends, the costs per project and needs of the buyers there.  

Cutting down timelines to not extend carrying costs Did you work with any real estate professionals (agents, lenders, etc.) that you'd recommend to others?

Despite these challenges, the successful sale at $87,000 highlighted the importance of strategic planning, effective project management, and strong partnerships in maximizing profitability in real estate investments with Partner Driven.

If it is not completed by a certain date or certain cost etc. then you can take over the project.

I wrote this out pretty quickly so there may be some details missing / closing costs etc but looking for some feedback on what others have done or would do here.  

Get plans drawn and get estimates from subs to get a total cost price for property.