Need some advice!! Starting a domain on a 14 year old domain

Hi everyone- I wanted to talk about and get your feedback about a directory that I will be launching soon. in 1997 I purchased a domain, which I'm going to keep secret for the time being, for a specific city like citystate dot com (Example: chicagoillinois dot com). Since 1997 this site has had some organic links obtained but not a ton. I plan to add the domain in a subfolder of the root domain, i.e. domain dot com/directory. At first, I will be the only editor and if it becomes more than I can handle, I may add more editors. This will not be a "everyone gets approved" directory. There will be a fee for inclusion.

Ok, so here's what advice I'm looking for:

How much should the review fee be?
Is putting this directory in the subfolder /directory a good idea?
Should I target any specific niches or make it a local style directory?

any additional advice you want to give would be greatly appreciated.

We are currently planning to charge $49 for review and inclusion. I've been contacted by a few SEO folks who have requested to be first on the list for inclusion. If I end up getting more interest than I can handle I will have no option but to increase the review cost.

Thanks again for your help.