[kevinelliott]

Otherwise known as fixed bid.

This is dangerous, in most cases, because clients are not looking out for you -- by definition they look out for themselves. It is not in your best interest to offer a fixed bid because undoubtedly problems out of your control will arise, and you are on the hook for it.

Furthermore, since the client is not always benevolent, you may be expected to implement changes outside of the scope of the contract, and this can often sour the relationship when you explain that it can't be done in the fixed bid you supplied. If you were upfront about a time and materials (T&M) beyond the agreement of the fixed bid, then you can protect yourself from this situation.