How this works
Small billing companies are often priced as a multiple of yearly revenue. The multiples are numbers you choose to test, set by default to a wide range. Your answers place your business within that range: specialty focus, no dominant client, long relationships, written contracts and an owner who helps with the handover all push it up.
This is not an offer or a valuation. Real prices depend on profit, contracts and the buyer, and how the price is paid matters as much as the number. See cash at closing vs earnout and how buyers value billing companies.