You are basically doing the work of a decorator / interior designer. There are many many ways to charge for this kind of work:
- PERCENTAGE The official guideline is 17% for interior architects in Belgium. Most interior designers will argue that a fixed percentage isn’t workable, because the designer will lose money if he actually does his job to find beautiful and money saving solutions. The only way to make money is to throw in a lot of expensive stuff.
- BY THE HOUR At the end of a built, clients once asked me if I could also help them with a color scheme and some curtains. Since I’m not a decorator and I don’t have these things in my office, I had to drive around a lot. Needless to say they weren’t happy paying me for driving around, although in the end it was still a ridiculous low amount. The problem is that clients don’t value your time and in general don’t have a clue about the time that goes into these things.
- PER SQUARE METER Strange all together. I never understood why someone would think that square meters of bathrooms, kitchens, living rooms or bedrooms take the same amount of time for a designer.
- FIXED PRICE Calculate the time you think you are going to spend on it, and present your client/friend with this bill before you lift a paw. Be very clear in your contract what is to be included and what not. If you don’t define these things in detail, there will be discussion about where your job begins and ends, and you will lose money.
- INTERMEDIARY You buy everything and sell it (at a much higher price, double?) to your client. This is usually the best way to make a decent amount of money, because in general people are only willing to pay big bucks for products, not for services.
Personally I would sit down with your client/friend and explain:
- In detail all the things that need to be done.
- How many hours you expect to be working on this project.
- What you want to charge per hour for this.
Based on this, fix your price, and while executing the job keep a strict eye on the time you are investing. If you’re not too concerned about ethics, combine this fixed price with getting certain percentages, going to your bank account, from providers.