If you make rap beats you can sell your instrumentals at Beats4tracks.com - Lots of music producers are selling their music online to artists that need instrumentals for their projects. When you make sales you can see what kind of beats artists are looking for and you gain experience as a producer.
Another option is to make your own website but you'll need to go through the process of designing and hosting the site. If you want to skip the technical stuff (automated cart downloads etc.) you could also send users from your website to your beat site profile to make purchases.
Nowdays there's lots of ways to get more people listening to your music by promoting yourself online. By using social networks you can build up your brand - you can also do email list building if you have a website. Once you have a good base of listeners you can keep them updated on your music.
If you plan on having a subscription to a beat website, having a longer subscription might work out better. Getting four sales in a year is easier than selling one beat every month, especially if you're just starting to build up your network.
You can get a free producer account at Beats4tracks.com