Kera-
I have been evaluating this business for a few years and have been looking for the right opportunity. There are a few things that I have learned that might help you in your decision making process.
1) It isn't passive in the way that real estate can be. With a rental, once it is up and running you can expect your monthly check without much ongoing effort and maybe a yearly turn over. With the coin laundry you need to expect to be at the store a minimum of 2 days per week picking up money. More often if the store is busy.
2) You will need an employee to clean and handle WDF unless you intend to do it yourself, if so plan on being their daily.
3) You are on the right track with pricing. Another way I have see them priced is 1x gross or 3-5 x net. In either case you need to verify income; meaning tax records, monthly receipts, utility bills etc. Because it is a cash based business some owners will say I made "X" but only reported "Y".
4) Make sure you have a long term remaining on the lease. You not only need to have enough time to make back the money on your investment but if the landlord decides not to lease to you any longer there is virtually no value in the business. You can take the equipment but where are you going to put it and how much is it going to cost you to move it? These are huge issues to consider.
5) Demographics are important and you need to run your business better than everyone else in the area to grab business from every other laundry you are competing with.
6) Lastly, and I haven't dealt with this but I have seen the numbers. This is a capital intensive business. If the machines are old you may need to upgrade them. Think $4000 per washer for the smaller units and closer to $14K per unit for the larger units. Dryers run $3500-7800 for single vs. double stacks. Financing is available for equipment but as with any investment make sure your numbers work.
Distributors are good people to talk to but remember their business is to sell you equipment so they see things through the rose colored glasses.
Good luck