Hey there!
First off it's completely possible! But before you make the same mistake I did when opening up an eCommerce store let me give you some advice
When opening up a forum, eCommerce store, Blog, etc. It's important to get a following so that when you open up you have people lined up ready to hop on your website from day 1 to give it that momentum.
For this I'd suggest creating a squeeze page for your niche that promotes a free product and deliver that free product through an autoresponder right away. After that have a newsletter that goes out 2 times a week that gives them really good helpful advice that they need.
Build your list this way and once you have a consistent amount of people opening up your emails and maybe clicking on links to articles they can read (this means you have an active email list).
Then create a social media page where they can join and talk to each other. This turns them just from your subscribers to a living breathing community that communicates under your umbrella.
Once you've built up a strong list and a strong following on social media it is then time to open up your store, blog, forum, or what have you and let them know you're working on it and creating a masterpiece. If you don't have the money to build it in this step you can always go ahead and do a kickstarter or any crowdfunding campaign (kickstart, indiegogo, gofundme, etc.) and let them know about your project and let them be your backers to help get this store launched!
Then once you launch and get the money from the launch day, then you have to know what to purchase and what to do to keep them coming. For this I'd recommend hiring a professional all around marketer and give him some of the profits (if you have enough, which you should if you did this properly... The pre-launch is the longest part) and let the marketer manage that money and give him the responsibility to bring in your customers with that amount of money.'
Then I'd also consider creating some sort of rebilling option for premium members to help even out your cashflow and make it more consistent
Hope this helps
Adam