Basically, you need to take all of your hard costs for one month (A hard cost is anything where you actually lay money for that specific item), so insurance, electricity, gas, software subscriptions, professional fees, cell phone & Internet bills, and add those to your soft costs (soft costs are things like money put aside for equipment replacement and anything else where there isn't a specific cost attached to it), and total those up. That's how much money your business will cost you to run each month. Now you need to add your salary into it and you have the amount of money that your business needs to bring in each month. We'll assume that total is $4000. Now figure out how many sessions a month you want to shoot - let's pick 8 as a nice easy number with which to work. That means every session has to bring in $500 AT LEAST. If you set your session fee at say $200 for a one-hour session, that means you need to push $300 worth of product from that session. Now it's simply a matter of looking at your costs for product and determining an average cost to get that $300. Don't forget to price digital files at a point where it makes prints look attractive. You want to sell prints and other product, NOT digital files.