How to Figure out Value of rehab-home before I purchase?

[Emilio Pereira]

Hello everyone, 

Question: I recently closed on a property for 215k. This is my first investment deal so I went in and dealt with a wholesaler (not sure if that was the best idea but here we are) and put down 5k (non-refundable) deposit into escrow. I did walk the property before hand, figure out the rehab cost and looked at the potential ARV. It all checked out with tight numbers but it was looking good. Lending was with a hard money lender I am using, 85/15. Right before closing the appraisal came back with a value of 195k, 20k under the number I signed the contract for. The wholesaler was not willing to negotiate the price and I was already in the hole 5k on the escrow deposit. I scrambled to come up with the 20k difference to make the deal happen. I did not want to lose the 5k deposit on my first deal and the ARV I got back from the appraisal was way higher than we anticipated, so I wanted this deal.

So my question is how do I avoid not knowing the as-is value of the property before I purchase to rehab?  Would it be smart to pay for my own appraisal before actually sign the contract.  Is there any books I could get recommended to help me better learn how to appraise a property myself? Just trying to avoid paying 20k over value price on a rehab property and not get stuck again.  

any help would be appreciated, Thank you all!