Its a good question... theres a lot of people who can offer you good advice on here
Its got to be something that interests you, you have to be dedicated and its good to have a niche market or offer something other people don't.
You have got to put the hours in too, when its your own business then it doesn't stop for weekends, doesnt stop outside 9am-5pm and doesnt stop when your poorly... Occasionally stops for stag doos
Be prepared for lots of accounting VAT returns TAX returns and spam spam spam in your inbox....
But its not all bad, ive grown up in customer service and logistics so I try to ensure people have a pleasant buying experience and in turn it makes me feel happy when the customer is happy.
I would also make sure you don't run before you can walk. So far I have not took a penny out of Tarmac Sportz, im looking at the first year as a learning curve, re-investing the money into this business and not taking any risks.. Ive learnt already that there are a lot of surprises and what you think is a great product and will sell loads of is not always going to be the case... and vice versa... my mate bought a thousand 'pets at home' dog leads cheap to sell on ebay... 12 months on and he still has 997 left ...
Ive asked the guys on here what they want, asked for group buy suggestions etc.... they know what they want more than I do so why not ask them..
These are just my experiences, there will be plenty more people on here with far greater business knowledge than I have but if you can use anything ive put then thats something..
Good luck