I have told many that having a plan costs less, which is usually the catalist for thier education.
Residentially speaking, the big hangup is usually lighting.
I will refer to lighting shops, who have lighting design people that will lay out a residence.
This works well, they'll spend all kinds of time in the showroom, then sell them a lighting package which i would rather not
IM(well....maybe not so humble)
Opinion, a large majority of lighting fixtures are so flimsey they border being a saftey issue...
i'ts not worth 15-25% to be married to.
Or, as in the case of my last rough out, walk around with catalogs and a magic marker for 6 hrs with mama, while the husband (not interested) smoked camel after camel.
Yes i charged for the time, never lifted a tool (other than the marker), yet went home drained from the excruciating procrastination.
I just recieved a set of plans for another post & beam, the owner wishes 10 recessed lights , unfortunatley there is no cieling cavity.(just 2" T&G)
Again, the party in question needs to be confronted with zeroooo's
before they take note.
Thus, i asked for an extended soffit, dragging all the other subs in with me, which resulted in a speedy response..
I'm just an EC,watching the whole construction world turning on a paper bearing greased with BS i guess....