If your husband is 100% with you, then I say go for it. If he doesn't want you to, please don't. Helping someone else is not worth hurting your husband. However, I think going through an agency would be better since they can help with all of the legal issues: such as "what happens if the biological parents refuse the baby because it's 'not perfect'?" Rare, but yes, it happens. Also, the agency can make sure your medical expenses are covered. With your private medical insurance, you may not have coverage for IVF procedures, just typical pregnacy issues as if it was your own child. This way you would have a contract with the agency AND the parents to pay for this. I have friends who are going through all of the hormone therapies to get the wife ready for implantation OF HER OWN eggs, but their insurance doesn't cover this. It's out-of-pocket at about $15,000 each time for the hormone therapy and the implantation. They've done this twice now unsuccessfully and will probably wait a couple of years to save up for another round. If you do this privately, you run the risk of the parents changing their minds about paying for the treatments, how much to pay you or even whether to pay you. Again, rare, but why take the legal risk. There are a lot of questions you need to ask yourself before taking on this venture. If you look up surrogacy agencies, they will be able to answer most of your questions and bring up a few you hadn't thought of.
I researched this because I wanted to do this as well a few years ago (for the coupleI mentioned). I never brought it up to them because it turns out I am a biabetic. I will always have high-risk pregnancies. I had enough fears carrying my own babies, I didn't want that fear for a mother who has no control over the body carrying her most precious miracle. I would have loved to help someone else receive that miracle.
If you are able to help someone else, and are physically and mentally healthy enough to do so, then go for it. Good Luck and God Bless you for your loving generosity.