If you want to stay bootstrapped, your only source of financing is sales, and only sales. As much as you have to be focused on developing a product of value, you have to consistently be able to feed revenue into the business. Without sales, you're finished. If you can't afford a sales rep, you should wear the sales hat full-time until you scale enough for you to hire a dedicated sales rep. I would consider offering equity to the developer so he's more committed and invested. This requires another form of sales - not to your customers, but to your team members and employees. As a founder, you're always doing sales from every angle.