You’ve surely heard the phrase “Comparing Apples with Oranges”.
If you change your design every time you interview a contractor and ask them to bid, then comparing their bids will be a worthless exercise. Each contractor will be bidding on a different thing.
Avoiding this problem is obvious: have a clear detailed plan and give the same set of prints to each contractor you ask to bid.
However, even if you give ten contractors the same plans, when you receive the bids you must look further than their bottom line price. You should not always go for low bid, assuming you will save money; or high bid, assuming you’ll get the best quality; or middle bid, assuming you’ll get the best of both worlds. Smart comparison means reviewing exactly what you will get for your money.
For example, if one contractor takes responsibility for mistakes, and has a built-in 5% allowance for unexpected costs, their bid will naturally be higher and still be a better value.
Or a contractor might be high bid because the other contractors left out portions of the remodel on the bid, relying on charging for change orders to finish the project.
Or a contractor might be the lowest bid not because they are basing it on cheaper materials or omitting parts of the project, but because they have an original and unique solution no one else has thought of.
The thing is to be smart when you compare. A good idea is to choose your bidding contractors by reputation and involve them in the budget. A good contractor can help you make the correct decisions that will allow you to stay within your budget.