for web hosting and domain purchases try,
Go Daddy or
Name Cheap(there's still more who can offer cheaper plans dr.google is your friend for that) cost depends on what package you want to get,
domains can be purchased for 1 year or more if you want, when getting your hosting you will need your credit card number or paypal for payment purposes.
if you want to integrate a forum solution to your site with you having a full control of its administration you need to have a software package like
PhpBB or
SMF installed in your site.
for a hassle free start, hire a web developer who will do the everything for you, a website is an investment and it's costly to maintain, getting people to visit your site is not an easy one.
some questions that needs to be answered first,
is my site an investment or just a hobby?
how can i get a return on my investments?
do i have a target market/users?
how many visits/hits does your site will generate per day?