And exterior last.Do you have any tips on how I can communicate with my contractors so I don't get screwed over? 

You want a title company who understands wholesaling and assignment fees or they might screw it up.The purpose of the title company for "simple wholesale deals" is that you can't really buy and sell a house without a title company. :) There is a lot that goes into the process, including making sure the house is actually owned by the seller, handling all of the money, having an attorney do the title transfer, etc.

Make sure you have a title company who understand assignments and wholesaling so they do the process right and don't screw it up and not get you paid.If you need documents, click Tools - FilePlace above.

Be honest and tell your seller that you screwed up.

Yes, we are talking to our lawyer tomorrow, but I'm going with worst case scenario and assuming that we screwed up.

Make sure whatever it is, it leaves you with enough room for screw ups and unexpected expenses. 

The only time I got talked into 50% down (leaving for a business trip out of country and under pressure to hire) was when I got screwed royally.Bottom line: contract it out and dont go with the cheapest guy either.

However, I don't want to get screwed or be "that chump from Socal" who the house flipper from the mid-west took advantage of.

If someone has to tell you "it's not just $1 per 12x12 tile, it's also cement board at $12 per 15sf, thinset at $20/50lbs, $10/200 cement board screws, XX for grout, spacers, tile saw blades,..ETC", then you are not ready to estimate rehab costs and should bring a professional with you.

Are they trying to screw me out of $250 or is this a legitimate cost?