TIME, Budget, Price
Often people misunderstand what the most important part of a flip is, I will tell you it is time. Nothing matters except turning the flip quickly. Actually every banker will tell you, get out of the deal and get your money working for you again.
Hold time will kill your deal faster than anything.
You have to own the house for some time. You have construction time, escrow and days on market. There is almost nothing you can do to improve hold time, except during construction. Construction is your best shot at making up some time.
First, have ALL of your materials. If your supplier is out of something, use something else. Adapt to what is available, don't fall in love with a tile and be willing to wait for it, with any luck, in a few months you will never see it again. Not having your materials will not only slow you down, it slows your contractors down. Contractors make money by being fast, if you slow them down, it is like you taking money from them.
Peformance based contracts.
When hiring contractors, offer performance based contracts. A performance based contract is a contract based on liquidated damages. If a contractor delivers a completed product early, they earn more money, if they deliver late, they are charged money.
Nothing will help your budget more than finding ways to cut time from your contstruction time.