My company has an online software as a service product that is subscription based (yearly) and when first launched, 3-years ago, has been more than doubling in revenue each year (in 2009, $2K, and in 2010, 5.9K). Expenses are low - really only hosting fees, which is about $600/year and advertising maybe another $500. This year I'm on track to make about 10K. Customer retention is pretty high, since the software stores the customer's data (I would estimate about 80% retention). Support is minimal and done part-time by me.
I'm interested in selling the product, which would include current customers. How would you value the product for sale? One might ask, why am I selling it? Well, I work full-time, and as my customer base grows, I may need to spend more time and effort catering to them. Are there licensing options where I wouldn't have support obligations but get royalty? What would you ask for the royalty?
Let's assume I am an investor. I couldn't even begin to guess how much to pay for your product because I don't know what it does. Furthermore, while you have had steady growth - it's easier to grow sales from 5k to 10k than from 5 mil to 10 mil.
Also, depending on the product/industry focus - a single change could wipe out the product. I would assume some serious potential problems. How much are you charging each customer? What levels are available? How many customers are you gaining each month? Have you experimented with pricing?
There is a lot of information that people would need to develop a proposal. Furthermore, I wouldn't want to pay you a royalty on a product this size without having you participate in a support mechanism. Its not uncommon for founders of products to be retained after a sale for 12-24 months in a support/consultant capacity because the particulars of every company are different.