I used to make coffee soap for my husband, using the second-brew method (re-using the grounds to brew a second time) OR using de-caffienated beans because he won't drink those. I am nothing if not frugal when it suits (not always, but in many ways). I also added dried-in-the-oven used coffee grounds for exfoliation. A little goes a long way with the grounds, though, so I learned to be more conservative on those. None of them ever smelled like coffee in finished soap. Coffee just does not lend itself to adding fragrance to soap.
Fragrance oils lend themselves very well to fragrancing soap, so I learned. Finding a coffee fragrance that pleases you or your intended audience, can be a fun journey, but also tricky. Tricky for me, because I hate the sweet milky coffee scents, although my husband does occasionally drink coffee with milk & sugar. Thankfully, not often. So it takes some experimentation to find the FO that suits. There are a lot of them out there.
I haven't made any coffee soap in awhile, because he seemed to get tired of it, plus he got tired of the dripping brownness of the soap in the shower. That could be avoided by just using a coffee FO and no coffee grounds and less colorant, of course.
As for salability of soap made with re-used restaurant cooking oil, some people do do it. There is a soapmaker who sells soap she makes from re-used restaurant oils in a nearby (to me) state. She participates in one of those historic old-towne-type places that have pre-industrial revolution skills demonstrations. I did not like the look or smell of the soap she made. She also did not label it in any way, which per the
Fair Packaging and Labeling Act is required for soap. I asked her about her process and I was so not impressed with the knowledge or claims made, that I did not even want to try the soap she made.
So, yes you can sell it, but I am not sure you'd get a lot of buyers.
Also, I've seen & smelled what restaurant fryer oil looks like over the course of it's use and when it goes into the collection bin out back where someone else on the food-chain (pardon my pun) comes along and collects it, after it's been sitting outside in this metal container for possibly a month or so (depending on the size of the town/city & other factors). Well, using oil like that to make soap really just turns me off. I don't think any restaurant workers I know or have known, would really want to wash with soap made from that oil.
Besides being an aesthetic turn-off, the possibility for rancidity is greater, so the soap would be more prone to DOS that soaps made with fresh oil.
Re-using one's own cooking oils is a more controlled process, and for personal family use, certainly seems fine. But the soapmaker has far less control over the cast-off oils from restaurants.