I’ve helped make proposals where I work, you gotta estimate how many hours it’ll take times your hourly rate.
I don’t know how our hourly rate is calculated but if I was in that position here’s an approach I just thought of.
hourlyRate = (hourlyLaborCosts + hourlyCosts ) * markupRate.
Hourly Labor Costs
You can see how much it would cost hourly to hire another developer for that labor with the required skills and experience. A fullstack web application on the MERN stack is going to be more expensive than a Wordpress site. Perhaps try Indeed Employer or Payscale to measure the larbor market in your area. Since you’re doing the work yourself and you’re the business owner this rate is negotioable…with…yourself lol.
All your expenses for the business broken down by the hour. Now most of these may be subsidized by your personal income (food, shelter, car) but developer related expenses should be in here. Computer, Internet, Github Pro or any other work related services.
For one time costs you can you do (price / 8760) because that’s the number of hours in a year. For example a $1200 laptop divided by 8760 comes out to about 14 cents per hour. I chose a year because that offers more attractive pricing and you’ll be claiming that on your taxes as a business expense for that year.
Your markup rate is really what you’re going to be negotiating with. That’s going to be how the business will profit after the labor and expenses. How you come up with this I’m not sure, but probably will be tied into your unique value proposition, competition and opportunity/opportunity costs. For example I would be more inclined to take on a lower markup rate if success at this project means having the opportunity of 3 more projects right after. I would propose a higher markup rate if doing this project blocked me from pursuing higher yielding opportunities and had no avenues of growth.
So then after all that, your price = hourlyRate * estimatedHoursOfWork.
Pricing is it’s own game too. Offer your client three different options. The cheap barebones option, the best value option, and the overpriced option. I’ve done this myself in my own business with ticket sales. I saw better conversions when I priced it this way. Misbehaving: The Making of Behavioral Economics, and Thinking Fast & Slow are two books that provide valuable insights as to what drives our purchasing behaviors. You can use that information to your advantage.
So after all this the client will be looking at a bill that’s probably in the thousands of dollars range. No one likes to see a $1,000 dent in their bank account. Ease the pain. Break it down into payments.
50% (negotiable) up front and then the rest into monthly payments so that the customer is looking at $83.33/mo over 6 months instead of a $1,000 price tag.
You’re getting into business and that’s where all the fun happens. Buy the book Business Model Generation by Alexander Osterwalder. I think that will get you the information you seek.