Database usesage

hello - on the V7 wot would be the most members you could have in total and online at once

and same wit the SQL cose i got a site in the planing stages and it'd have about 50 members, maybe more but wouldnt be that active for a while, so i could get the funds for a SQL and was just wonderin about wot a Access database could handle - thanks

*edit*

forgot to add, is it possible to have 2 have 2 forums on 1 sql database?

or anyway of havin to forums on 1?