looking for a theme to support my needs

I’m new to wordpress. My organization runs an alternative currency, like a formal barter and trade service. There are hundreds of traders and service providers, who trade with our own local money.
I’m looking for a WordPress theme that will all any service provider to log in with their own password and change the details of their listing. So, if I were a massage therapist, I could go to the site, log on, and change my details, like price, hours, or profile, yet I would only have access to my profile.
Is there a theme that would allow this to work. What we have now is at https://www.riverhours.org and we have to always change a service provider’s information ourselves! Too time consuming. We need a site where the traders can go on line and change their own information, but not alter the web site.
Thanks.
Scot