heck, you might even be able to work out a gig where you can interrupt your contract to be with your customers if you need to. if you have unusual skill (or are willing to work for below-market rates) you can usually find someone willing to be flexible.

that said, you obviously have a limit on the total time and effort you can put into a day so that might not work if you are already coding 8 hours a day on your product. but if your product is 'pretty good' and you are mostly marketing and waiting to be noticed, it might make a lot of sense to shave some hours off to sell to other people.

But then, most of my marketing is 'do something to try to get noticed' - i imagine if most of your marketing is cold calling or otherwise direct customer interaction, then it might not be so easy to take hours off.