Where to begin
Plan your project out as best as you can with as many specifics as you have available. Select everything that you will need in the new space from lighting to flooring to major appliances. Write down the model number, color and size of each item so you can include this information in the contract.
If you are concerned about price, this is one place where you can economize, shopping for items that look and act like the higher end items without the accompanying price tag. However, if quality falls off sharply along with the price, go with the higher priced item...it will be cheaper than replacing a defective or badly made item later on.
You might want to think about accomplishing the project in degrees to be able to afford the project. However, sometimes this will add to the total cost in the long run.