I thoroughly agree with the others. Here are my additions.
A one man show will be around as long as that one man is healthy, content and able to work. There will be no legacy to hand down. Nothing of value to sell. That one man owns a job, not a business. I'm not knocking it, many are content with working hard and making enough to pay the bills and take a vacation every year. The business model of a one-man show is very fragile. You may go your whole life without someone running a red light and T-boning you at 40 mph. Then again, you may not. I understand that no one can start off with ten employees but you have been in business long enough that you should not be out cleaning at all. You should be out selling, marketing and building relationships with large accounts. Marko, I suggest you get a book called E-Myth. They also have it on audio tape. It will be the single biggest life changing book you will ever read or listen to.
Whenever I explore growing larger I look at the diminishing return on adding crews. Josh said it perfectly. Just because you double your workforce, you do not double your profit. Its always a better idea to raise prices. It sounds like you are priced too low, Marko. Most of the one man shows price too low. Why is that? Because they do not think ahead abbout the time they will need employees and to create job positions like sales, operations managers and foremen. Those are the things that a BUSINESS may require.
You are a young guy. You are also smart enough to understand that you are going to wear out. If you are looking to hire someone it is because the work load is getting too great. Start by raising those prices. Yes, some restaurants may drop out but so what? You will actually make more money working less. As your book builds back up, you will then have the proper profit margins to begin hiring employees and your wife won't notice a thing becuase you will be making the same money you are making now.