One way is to look at it as an investment. And, how this investment may stack up against other investments. Say you have $100,000, you would expect a $10,000 return on that $100,000 if invested in something that "promises" or is "expected" to return 10% on investment.
So if your business has a net profit (yearly) of $50,000 (return), what investment is that worth? At $100K, that's a deal. At $2M, this return you can get from a bank.
This will at least help you put it into perspective, just to see if it makes sense from an investment point of view.
Existing accounts should be considered for their impact on investment (good vs late payments) if not already factored into the net profit equation. And then there are assets or lack of assets, debts, and backlog which could change the value quite a bit.
You might ask a busines broker how he goes about valuing a business. A lawyer will want a hell of a lot of money just to kill the deal. And to make the deal happen, multiply by 3.