Reading between the lines, I think you are after the pros and cons of SE. I'm currently SE, so I'll have a go!
Pros
Generally speaking you will earn more than someone employed.
Your time is your own...if you don't want to work, you don't have to and can pick your holidays (we're off for 5 weeks soon).
For someone like your OH, you can go and work for another subbie pretty easily.
Cons
You have no job security...if you don't work, you don't get paid! There is no monthly wage to fall back on. Remember, this includes illness (even if you have a cold, you might not work) or injury, and of course no paid holidays!
You have got to sort out your pension, income tax, NI stamps, VAT payment (if you earn more than £71,000pa). Most of this I do myself, but have my accounts done once a year as I don't profess to understand the tax laws!
Overall, you have more flexibility SE, but no security. However, lets say the building trade bottomed out even more than it is now and your OH had to get a job working for Mc Donalds (for instance). Thats OK, as working as an employed person for part of the year is a contingency allowed for on your Tax Return, so its nor like you can never work employed again. Has he got anyone he can talk to with personal experience as a brickie? I've been SE for 18 years now and have no problems. Like anything else, if you wait until the figures 'add up' in your favour, you'll never make the jump. Go SE and you'll probably be OK. I had a quick look on the net and there is a lot of stuff out there. Have a look at
http://www.adviceguid...loyment_checklist.htm
You would want to be looking at the 'Sole Trader' stuff (assuming he is not employing anyone else). Good luck!