This is a question I get asked a lot from our peers. And it's a difficult jump, so let me offer some reassurance. Also, if you keep doing the same thing, nothing will change. So here it goes!
You have to create the structure before behavior will change
This is cheesy, but you really do have to have the foundation poured before the house can be built. And your small business is no different. You want to grow from being 1 or 2 people, but it's hard to make the jump when so much is on your plate.
Make an org chart
This sounds so silly, I know. I didn't do this for years. But when I did, it brought reality to everyone, myself included. Make an org chart that has each role first. CEO, COO, CFO, Sales director, Operations director, Finance and HR director, senior engineer, engineer. Once you've made those boxes, put a name inside of each box that you do. Once you count how many times your name appears below a box, you'll realize just how much work you're trying to accomplish. You have to see this problem before you are motivated to take the next step.
Change the names
This is the fun part. Giving others a chance to take responsibility. And I know there's not enough money to promote. Tell them that too. But if things are going to change around here, more people are going to have to step up.
And if you are running solo right now. Write "New Hire" next to each box that you want them to do. Yes, even as a new hire you can totally have them lead parts of the business. That will fire them up and give them even more excitement about the role. (If they're the right person. If not, then don't hire them!)
And who's going to do the work that you're not doing?
This is the part that feels risky. And you won't know it until you try it. The truth is that many of your assumptions of how fast work must get done are probably not accurate. I used to try and get every client request resolved immediately. But it wasn't until I let emails sit for a few hours that I realized most client requests can be addressed later in the day, or in two days! Obviously certain cases are more urgent, but you probably have more wiggle room than you think.
One thing that held me back for years was the fear of delegating too much. That in turn held back the entire company. I learned that you have to let others tell you when it's too much. That's their responsibility, not yours. So you must take your hands off the wheel and see how far they can go without you. I think you'll be surprised how much they can get done. It may take a few weeks for them to settle in, so be ready to answer their questions. But go for it. You won't know it until you try it, and it could be the one thing holding you back from growth.