Back to topic, for the OP.
We're still in the finishing up stages of doing and office/shop/apartment.
Doubt many can afford to do what they want, and even doing what you can is maybe more of a quality of life thing, than making financial sense.
Anyways, we had all the arguments posted here. Didn't want the noise or dust, or employee access to business stuff they maybe shouldn't see. Spending more money, when everybody already has an office at home, etc. etc.
But in the end, with 3 of us partners all having stuff at home. We wanted all the business stuff together, and then there's the Mice Will Play While The Cats Away. Figure we'll get more out of the help if we're putting in the hours in an office, vs going home and leaving them unsupervised. Plus it gives a place to meet with business people who come out like insurance, bank, etc., vs meeting them at your house.
So with money, or lack there of, plus tight space requirements. We did a two story office/aparment in one end of the shed. We pushed the numbers on every conceivable way of doing it, and this was the only way to fit our budget and space.
Lean to would probably have been better and in budget if we had the room. Seperate office while not tons more money, was enough more that there was no way we could make it work.