[bbcbasic]

I would recommend first seeing if it is worth your while. You may find that the freelancing rates you get will be much less than your day job, once you take into account the time and money you spend on attracting clients.

One way to do this is via a minimum viable product. E.g. print a flyer and offer a price that is reasonable to you, and post it to 1000 businesses, see what response you get.

IANAL, but you can probably worry about the contracts and invoicing once you get an order. In-fact start off with small jobs, send them a quote and just get them to pay in advance. Send an email invoice is probably good enough. Not sure what country you are in, but usually you can do a small amount of business without registering as long as you declare it on your tax return. But research this.