I'll agree with a lot of the above in saying it depends. How's that for taking a stand?

In my own business which is essentially a service business there was very little start up cost so in very short time I was profitable. I still have a long way to go though to get the profit I want.

One of the factors especially with a service business is the network you already have. To vaguely answer your question Lisa if you already know a lot of people looking to rent apartments you can probably profit rather quickly. If you don't already have this network in place it will most likely take longer.

Chris since what you're planning on doing is related to your current work you may already have a network of people who can recommend you and help you build your client list.

I think you're taking a good approach though in spending time planning before getting started and in doing what you can to be realistic. Be prepared not to make that $30k at first, but also believe in youself and your business that if you keep at it you will get there.