I did a bit of research on this subject myself as i came across the idea too.
Only problem is, That most dvd license companys, i dont know if this is uk only but only allows you to show them to members only like a film club. where you cant show film times charge admissions etc to the public.
Spose you could charge a monthy payment to the customer etc which they pay for memberships.
A digital projector would be the best idea.
Depnding on the size. and budget of our cinema a normal standard projector off ebay
http://cgi.ebay.co.uk/Muti-Function-Digital-Home-Cinema-LCD-Projector_W0QQitemZ130170504469QQihZ003QQcategoryZ22610QQcmdZViewItem
could be of some use. But dont expect a good picture.