Now, if you are familiar with this type of investing it can be very lucrative and literally lead to vast wealth. 

If their credit history is sufficiently long to generate a reasonable score for them then the credit score tells you the answer! 

.: No longer a rule, just a ghost in the past, A relic of days when profits were vast.

@Michelle SharkoAnswering questions in step by step fashion:- Is it a good thing to do or not is a personal finance decision and it depends on the person asking it, their risk tolerance which in part has to do with how this HELOC or line of credit works and how your personality fares relative to taking on new debt (a person more adverse to debt might have sufficient savings and temperament to pay down/back the debt versus a financially liberal person might get in over their skii's as).

no way to really answer this until we know what state or counties you want to do these developments in.Each state and County can be vastly different and as such change the metrics of that whole laundry list of questions you asked. 

Yeah, insurance is likely more than sufficient for most investors.

You are off to a great start because you know you don't want to LEAVE your job to do real estate, you want real estate to be a sufficient side car to the job you are already crushing out of the gate.

Otherwise taking detailed videos and pictures for the contractor to get a good idea of budget should be sufficient to get a realistic budget. 

A higher ratio (typically above 1.0) indicates that the property generates sufficient income to cover the debt, making it a lower-risk investment for lenders.3.

This is actually one of the main reasons many agents and investors may not like them generally speaking (they are often not serious professionals with a proven track record of success, the vast majority are struggling to find their first deal and are time-wasters to interact with).