How many topics can I create for this type of forum? is there a limit and would there be problems if I created too many. Fore example 1000 total topics for a local town directory that lists all services and businesses ?

1000 is not a problem. I host a forum with 15,000 topics with a total of 120,000 messages so far. I don't know if there is a max though, but I don't think there is.

maybe I was referring to the forum Titles instead.. not the topics....

If I have that many forum titles on the home page it would be a massive list that runs downward for pages and pages so deep down the page, but i guess if it is only text it would not overload the page

trc4949
No limits for this, but keep in mind how it would look on the client side if it's massive... not sure it would be user-friendly.

We have customer forums with millions of posts running fine, here it all depends on the powers of your server, specially memory and disk size. MiniBB is quite compact and simple when serving the data, and it could handle a lot of traffic.