Depends, I started out like this with cars etc. Essentially if you do it properly and don't irritate and annoy your neighbours no-one will know what you're doing. Only buy things which look clean and presentable- you can earn a very good amount by only selling 3 cars per week on ebay- pick things which are an easy and quiet fix like something which needs a new alternator, starter motor, etc or which has just been stood and the idiots therefore assume it's a non runner. Then and this is important get a work shop as quickly as possible because however considerate you are someone will have nothing better to do than cause as much aggro for you as is physically possible even if you don't bother them at all. As for Tax, you need to declare any earnings but you can lose a lot in terms of what you can claim back, but you'll never get planning permission for this so don't even try.