An interior designer COULD be expensive. But then again so could doing it yourself and making a mistake! An experienced interior designer could minimise significant risks on a large interiors project that you have coming up. Would also free up a lot of your own time to do something else. I guess though many end-clients fancy themselves as interior designers so actively want to do it themselves. A good service for a true interior designer to offer could be a MENTORING SERVICE where you help such people and then you are in the right palce to take over if it all goes wrong. you’d get paid for it for no risk and you would get to advise on the creative bits rather than get involved in all the nitty gritty non-creative project management.