Free is Good But almost always Comes wth Ads ,, banner , text tara and others.
Option 1
With little or No HTML PHP Knowledge you can setup a Fairly Attractive site and forum
http://www.freeforums.org/
Option 2
Got a Server ???
http://www.phpbb.com/
http://www.simplemachines.org/
http://www.yetanotherforum.net/
http://www.mybboard.net/
Host your Own ,, This requires DB, Forum, and Prob some PHP knowledge to get everything installed and working correctly .. PHP is free software and alot of people use it due to the community support for coding and making it Custom. YAFF is also open source but is limited as a portal site.
there are others just google Forum software
Option 3
Find a Co. to Build and Host your Site
This can be Expensive.. 100s of dollars to get the site built
most programmers get between 60 and 80 buks an hour for Coding
and then a monthly or yearly cost for hosting the site .. Avg 70 to 100 bucks per year for good hosting with storage and unlimited bandwidth
The Down side to Option One is you Dont have access to an Un-Encrypted copy of your DB.. which means if you decide to move your Community at some time .. you will be charged anything from 50 bucks and up to get a copy you can inset into new software.
The other two options give you full Control over your site material and everything on it but it will cost you monthly in the form of a server to host it on ..