Nice! That's a pretty good idea. I'm staying under the state limit for now but once I retire I plan on growing my flipping business alot as I'll have more time to search out and find the deals. I always love to hear the benefits of it as far as taxes etc. For now it seems that Uncle Sam would just be taking 15% of my profit.
I have an online business sort of like you have there, except mine is geared towards Yamaha ATV's and side by sides. I'm looking to expand it eventually but the online parts business is tough unless you can come up with unique parts/ideas that fix a common problem. OEM parts are tough to sell against the big guys. Basically, I sell parts for the Yamaha 4wd system. I found a way to repair and replace a common problem part for around $50 vs $400 which is what it would normally cost. Like you I contract out the manufacturing and I market the parts on ATV forums. If I'm not out of line, here is the link if you want to check it out.
501 Parts.com Yamaha 4wd System Repair Parts & Service
I enjoy this and it's a good way to bring in a little extra money also. I sell the same parts on Ebay and Amazon. Hopefully it turns out to be a good supplement to retirement.