If your employer wants to move ahead with the project you start, there would definitely be a conflict of interest if you left to develop the same product on you

If your employer wants to move ahead with the project you start, there would definitely be a conflict of interest if you left to develop the same product on your own. You'd also have the issue of potentially using trade secrets from your employer. In any case, if you get sued by a large company with lots of lawyers, your business will probably die even if the lawsuit has no merit - you could be bankrupted by your legal fees before the case ever reaches trial. Also, unless your manager is the CEO or CFO, they're probably not authorized to negotiate deals like this for the company. They'd have to get your proposal approved at the highest levels. As with all legal matters, you need to consult an attorney who practices in your state, and you need to do that before you make any contact with your employer on this.