Difficult?? YOU BETCHA!!!!! Acccckkkkkk! I did that for SIXTEEN LONG YEARS..I did enjoy it most of the time, however, you have to understand that most design clients are "middle" to "upper" class...and have DEMANDS..that will drive you NUTS! I have had clients CRY and pitch a FIT over a sofa that was specially ordered, and did not come in in time for their big party/holiday/whatever...OR...
You get someone who comes to you with a HIDEOUS gold velvet chair that is ratty and worn, and want you to design their room AROUND that CHAIR! OR, try as you might, you tell them something won't work, or won't look good...they don't listen, do it anyway, it looks like crap (as you warned them it would) and they blame YOU anyway!!!! Or...you order carpet/wallpaper/drapes and they come in the wrong size/color whatever...and YOU are blamed (after all, YOU did the measuring)....
I got extremely burned out after 16 years. I no longer work in that field. Your best bet, if you still want to try it, will be to intern with an established designer, or with a high-end furniture store that offers design service..and intern there..
It may be helpful in your decision to shadow an experienced designer, BEFORE you commit to a career, so you'll know whether you are cut out for it....
Larger cities, where there is "money" will bring you the most chance for developing a clientele.