Processing herbs is a shitton of paperwork in most countries. Except drying, which actually gets you less income than fresh herbs, since you'll need to compete with large farms.
For example, for oils (or anything based on them), you'll need a still. Here in Germany, that's feasible - you just need to sign a contract guaranteeing you won't sell moonshine without paying tax. In Czech republic, not even that. In cucked nations like the US, you'll need to get a license which you'll constantly have to renew, and pay for each time.
Then, if you want to sell the oils as "aromatic oils" for food or medicinal purposes, you'll have to pass inspections. In the EU, you'll also have to get an identification number for every medicine - most oils are registered already, but if one isn't, you'll need a doctor or engineer to write a definition and recipe in order to register it. Bit of overkill imo, but seeing how many retards will build their stills with lead solder, it's sadly necessary.
With general foodstuffs, like aromatized vinegar, you'll have to learn about the legal requirements for those and may have to pass inspections. Not that hard - I learned all requirements in a few hours, and my only inspection in 10 years was "Hand in a jar of your product, and well check for contaminations". But in theory, inspectors can demand to see your production rooms at any time in most countries.
of course, if OP is in Somalia or somewhere like that, selling processed products is best. Though in that case, he might as well go for weed and moonshine.
But in the west, fresh produce and honey are the only things that really make sense on a small scale, and herbs have the best money/work ratio.