First off, Bob is not here. Second, if Bob was, he would need more information explaining exactly about your husband is trying to do, before he could try to answer your question.
So, my advice is to explain to us (non Bob) exactly what it is your husband is doing (with details), then we could assess whether or not it is a good idea. We need to know what will be supporting the load of the house, what the purpose of the steel is for, the guage (thickness) of the steel, climate in which you live, how much will be below grade, etc., etc.
Describe what steel is a lot cheeper than. What type of basement you have now. What is he really trying to do?????
Has a structural engineer given his blessing for the project. Have you considered the expansion and contraction effects of steel. My only advice can be to describe your plans with a structural engineer and get his opinion.