I used to work for a decent internet cafe in Maritzburg which in it's time became the place to come and lan for guys whose gaming pc's weren't up to scratch. Our charges were R15 for 1 hour, R25 for 2 hours and then R50 for 5 hours. We were in a central location for a lot of schools and the University so a lot of guys would come after school or between lectures. We also sold snacks and stuff at basically cost price so guys used to love gaming there. At it's peak we had 24 gaming machines and 8 office pcs.
You don't need the latest machines, but at current prices, you'd probably be spending a minimum of R6k per machine, to make them relatively future proof.
Decent screen R2k
Decent gfx card R2k
Rest of the bits and pieces R2k
I recommend you get in touch with Valve and sign up for their Internet Cafe subscription service which gives you access to almost the entire steam library for a monthly fee.
But just as a warning, unless you already have a demand for gaming, I wouldn't recommend it unless you have a lot of $$$ to spare.