There might be other costs like appraisal / BPO, property inspection etc.Few lenders give 50% of construction costs are post reimbursements in draws and few does higher percentage of coverage on renovation costs.Ask around and see what works best for your situation

I've heard of certain companies out there that will challenge your assessment on your behalf but they usually take a percentage of what they save you as payment.

@Jason Turgeon Well, what I've done so far is I look at the Zestimate, and I also look towards the bottom of the listings for the percentage above or below the average market value. 

I calculated the ARV by taking the purchase price and then used the percentage that zillow expected the house price to increase in the area the house is located in. 

Any home equity line approach would on a percentage, i.e., leaving a margin for market downturns.

SFR and MFR are killing it currently and pose much less headache when it comes to getting them to cash flow or pay out.

I have limited capital for an emergency with my current property, life etc... that I would prefer to retain for just that, in addition to possible closing costs, inspection, va appraisal, and most likely a percentage of vacancy, and mortgage of said new property.

The percentage of people who buy programs and actually invest is very small.  

If so what percentage of the total amount ?.

The offer is 125k, if appraisal come back at 118k, will lender do the agreed percentage on 125k?