I have learned my strengths and weakness and accordingly have built up a network of people who can provide services for which I am not 100% familiar and we thus share the revenue or come to an agreement accordingly.
You need a team of players in this business to cover the needs of your clients, especially business clients. When the client's server is down you had better be available to handle it. That being said, the best way to handle the situation is with a 'partnership', partner with another tech who can help handle the load.
As was mentioned, a business client is one who sends you a monthly check, and to service that client you need 'tools' to do so, such as a proper billing/quoting/ticketing system and remote monitoring software, and the good 'tools' don't come cheap.
Also, if you are going to 'take the plunge', get those business clients signed up in advance. Work from home, but make sure you have a fabulous internet connection. We work primarily from our house and do a lot of remote support. We have Fios internet (35u/35d) and also cable internet - neither 'package' includes and TV. If one system goes down we can use the other system. We wired the whole house. Our living room has 3 professional tech benches and a workstation for our otherwise outside tech when he drops by. The way the house was built, it came with an office just inside the front door where the majority of the remote support is handled, and it has a large 'L' shaped desk setup with 4 monitors. What is really nice about this house is the skylights that are in the living room and the family room, in the hall bath and in the hallway so we don't need the lights on during the day to work.
So, if you have the right setup at your place, you can find a trusted partner, have businesses signed up and bring in the $$$, have all of your 'tools' in place and know how to use them, then I think you can start planning on when to make the move to 'business owner'.
If you feel the need to 'borrow' money I suggest it be for an investment in your company for something that you resell, like storage space (NAS units that you put in businesses).