I too am a US citizen living in the UK. I am however married to a Brit; we were married in Las Vegas before I moved to the UK. Nearly 3 years on now, were are at the end of our US green card application. We went through the process on our own, nearly without an immigration lawyer, but it's been very, very aggrivating. I would strongly encourage you to hire a lawyer to guide you through the very complex process; (link removed by admin) We had to contact them for help overcoming prooving my US domicile.
You may consider marrying in the US first, before applying for his US green card. There is a 2 year differential however in which his green card will have extra conditions on them that you'll have to proove to have removed, in order to keep it. After 2 years of marriage, there are no conditions on the green card.
Speaking of domicile, have you ever lived in the US? (are you a dual citizen?) If so, you will have to re-establish your US domicile. This is not an easy thing to do, which is why you need a lawyer. There's work to be done, by you, before you start the application process: bank account (keep active), job offers, education, investments, property.
You really need to do your homework if you go through the application process on your own. I personally don't recommend it although my husband and I will get our approval on the 30th. We've had lots of stops and starts along the way and more arguments than I care to mention. It also costs quite a bit of money. Nearly every document you need send in requires a fee to be paid and special couriers to handle them. I'm not sure how much we've spent so far but I'd venture to say it nears $2500-$3000 USD, maybe more if you convert our pounds spent into dollars.
Starting a business in the US requires a TIN/SSN (taxpayer identification number) and I think there's a fee tocon pay upon application. You'll just need to research this as I've never started my own business. But as neither of you will have any establish US credit history, plan on paying her than average fees for insurances, deposits, etc. You really should walk before you run and get your feet established before trying to start up a business. Just my opinion though!
The qualifications may or may not transcend for your soon to be husband. But, as we all know, the US is land of the free and you can do what ever you set your heart out to do; anything is possible if you work hard enough - this is a HUGE cultural difference between the US and the UK, again, my opinion! I don't know where you're planning on relocating to but it would seem to me that the more sunnier and warmer climates would benefit his type of work. I'm from Phoenix, AZ and people there are very body conscious so work there is plentiful for someone like him. There's also an important military base there so he could establish himself in that 'family' for an easier time of it.
I could go on an on but email me if you'd like to chat more.