I run a business from home. The first thing you need is a clear business plan then you need to find an accountant, register as s/e with the Inland Revenue and tell the National Insurance people so you can pay your contribution direct. If you don't do this then the Inland Revenue fine you - they do NOT have a sense of humour about non payment but are extremely helpful if you ask them for advice. You need to check with your Landlord (if renting) or whoever lends money on your house to make sure they will allow you to use your home for business purposes and you may want to check with your Local Authority to find out their regulations about Council Tax. If you are thinking about anything to do with food then (personally) I wouldn't bother because it is just too much hassle.
Do you know what kind of business you want to have? If its selling something you need to think whether you have a reliable source for your stock (preferably at least 4 different sources for stock).
I didn't make any regular money at my business until I'd been doing it for six months. Luckily our savings covered my start up costs - its best to try and start without borrowing any money (there is nothing worse than trying to service a loan while your business is just getting off the ground).
If its internet based then you need to assess your skills and abilities - will you need additional possibly technical knowledge about running/designing a website and submitting it to search engines, etc.
The plus side of having my own business is not having to answer to anyone except my customers and I can work the hours I want. The downside is that even when I felt
awful with flu I had to honour my commitments and crawl out of bed to get on with my work and - of course - you can't rely on a fixed level of income.