People are always looking for a fun evenings entertainment or ideas for a birthday party.
Typically a track can accomodate 10 karts. During a evening you can have 3 separate sessions (5-6, 6.30 - 7.30, 8 - 9) That would give 30 paying customers per evening paying on average £30 for an hour long session.
There is also potential for daytime corporate sessions.
On the weekend there would be potential for 6 - 8 sessions.
A track of this size could be run by 3 or four people depending on the layout.
There is also extra revenue from snack sales and photographs.
All you would need is either a inside or outside space of around 300 Sq M and 100's of tyres to form a track. (tyres can be obtained free from tyre fitting garages).