Yep, and you need to look after your site and members daily. My site I got a year now and spend contless hours on maintaining the site as well as my members. I got a 1000 members and did delate about 900 who didn't log-in for over 3 month.
You will have to invest if it is for your pleasure or for business it doesn't matter.

Its not just putting a community site there and people will come,