Help on investing in small businesses please.

I therefore have a friend who wants to start her own business, but she needs capital.
I am willing to give him the necessary capital of £ 2,000 for a 15% stake in the company …

I have no idea what I'm doing !!
Iv has never invested before, iv has never run a business, I have some spare money that I would rather invest in someone rather than sitting in the bank.

What should I do when it comes to taxes?
What type of contract should I create and how can I create it so that I do not get bitten or even get kicked out?

Help on investing in small businesses please.