Hi welcome to the site. It's fab.
You will have to get your insurance sorted before you start on paying clients, I get mine through BABTAC if you go on there website you can see the different covers and prices.
You will need to keep all your reciepts and keep a record of all costs and money recieved, if your only part time it doesn't take too much. If you know anyone else self emplyed you could ask them to show you how to jot it all down. You have to declare you are self empoyed within 3 months I think, you will then be sent a tax return when it's needed.
Obviously you will need to do yourself a price list, get some done by vist print there very cheap but look good. They also do websites, ive found having a website has really helped boost my business. Get a free ad on all the free sites, ie, google, yell.com, netmums, scoot, there are loads. So when people google mobile beauty thereapist in your area you come up. Then they can take a look at your website, people like to see what you have to offer and prces before they contact you.
Hope some of this is of some use to you hun, enjoy going mobile, I love it.:hug: Good luck.xx