First let me apologize about the length of this post, but I'm going to try to give you a good runnng start.
If you want to be accurate, you need to figure out what is called your 'fully burdened shop cost' as if you were running a full-time shop. Do you have an accountant? They could help you do this, but it can get very detailed and costly.
Here's a VERY 'quick and dirty' way to get a 'ballpark' idea for a one-man shop:
1. Add up the replacement cost of all your tools and equipment. If you have an inventory for insurance purposes, that's a good starting point. Let's assume that number is $60,000 - which may be way low or much too high for your situation.
The IRS will allow you to amortize this over as little as 3 years. That means
Tools and equipment cost =
$60,000 over 3 years =
$20,000 per year = $9.62 per hour (assuming 2080 hours per year)
2. Estimate the square footage you would need if you had set up shop somewhere. Now, check your local newspaper, real estate listing, craigslist or whatever to see what a space that size is renting for. This will vary widely, but in your case it will be VERY COSTLY because of the boom situation. Let's assume a space will cost you $3600 per month and includes utilities to simplify our calculations.
So Space cost = $20.77 per hour (assuming 2080 hours per year)
3. Add the costs of an accounting system (software and computer and printer to run it on), telephone, internet, etc. Let's say that the accounting system costs $6,000, so
Accounting System = $0.96 per hour (assuming 2080 hours per year)
Let's say that the services - internet ($50) & Telephone ($50 - you have a cell phone, don't you?) & garbage ($20) & accountant ($100) & business insurance ($400). Monthly services cost = $620 per month so
Monthly services cost = $3.58 per hour (assuming 2080 hours per year)
4. Vehicle - may or may not be needed. For simplicity, we'll assume a 3 year lease with all repairs covered by warranty. Assuming a medium sized truck, van or SUV, Monthly = $1,200 (yes, that's a real number!!!) so
Vehicle lease = $6.92 per hour (assuming 2080 hours per year)
And this does not include fuel costs!!!!
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We could keep going and getting into more detail, but I think you get the idea. So far we know that your hourly 'fully burdened shop cost estimate' is $41.85 per hour, broken down as follows:
Tools and equipment = $9.62 per hour
Space cost = $20.77 per hour
Accounting System = $0.96 per hour
Monthly services cost = $3.58 per hour
Vehicle lease = $6.92 per hour
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Fully burdened shop cost estimate = $41.85 per hour
Insert your own numbers, make your own assumptions, and figure out a good 'guesstimate' to begin working from.
Hope this helps!