to know if your proposed car wash business will cover the note and all the expenses including your salary, you need to create three years of cash flow projections. You need to start with the daily traffic count and use a multiplier for your hopeful average of cars per day. In my business plan about 20 years ago I plugged in 3/10 of 1% of the average daily traffic count in front of my site. I struggled a lot at the beginning because I came nowhere near that number in actual cars washed. There were several factors involved. My speed limit was a little high out in front of my site even though I thought my egress was good. I was running a machine that although it was affordable proved to be problematic right from the beginning and I found myself doing a lot of repairs and re-engineering and honestly I was in way over my head.
Many of the expense that go on your cash flow projections can be obtained but it takes some work. You have to find out what your taxes will be, what your insurance policy is going to cost, you have to get an idea of chemical cost based on your sales projections, you have to factor in things like licenses and permits. Then you have to factor in for things like cost overruns on your construction which in my plan I used 20% and that really helped when I reloaded my automatic wash a few years ago.
The other thing that is important is that when you create your cash flow projections you do a worst case scenario, a best case scenario, and Hopeful average.
In my mind, this is the right approach for almost any business. You have to start with a business plan. Any other way is asking for trouble.