It's certainly POSSIBLE to sell starter, people do do it after all. Sourdough.com sells starter, but they have a large selection of "starters from around the world" so people will buy multiple kinds, plus their book. King Arthur Flour sells it too, but it's just one of several hundred other products, a minor one at that and they sell a fancy branded ceramic crock with it. Customers will come back for flour and other goodies. They also have a huge bread baking audience, massive branding power and it's a small item in their overall inventory, not their "bread and butter" if you'll pardon the glaring pun.
Then again, Friends of Carl give their 1847 Oregon Trail starter away for free. NY Bakers sells theirs but will also give it away for the asking with other orders.
Can you sell it? Probably, sure. You will find small websites selling their own starter. Can you make it a viable business, even if a small side business? That one's a bit harder to gauge. You'll need to do some number crunching and see if you can make enough sales at a low enough price people will buy and still make a profit after costs and retail margin.
Are there enough potential bread bakers in the area to sell enough units to make a fair income after all the costs are accounted for? Can you re-sell to these people or do they now have a perpetual supply of your starter?