Wow, behold the thread drift. Now we're on Spider-Man! But meh, why not?
And actually, no, the only reason Peter isn't as rich as his talent would allow him to be is Plot-Induced Stupidity.
I read the storyline where Peter can't get rich off of web fluid adhesive because 'it only lasts for an hour'. *headdesk* A super-adhesive with a time limit for wearing off actually has a crapton of uses. Chief among them would be tangle-web shotgun shells or grenades for use by riot cops, the ability to restrain people without actually harming them. Tony Stark actually patented and sold 'tech-foam' in 90s Iron Man for the same purpose. As near as I can tell, Tony made a shitload on it.
As far as 'how could Peter do business without exposing his secret identity'? Well, cripes, two easy options come to mind;
* Give Matt Murdock his power-of-attorney to conduct financial business for Spider-Man. Lawyers cash checks and sign paperwork for other people who won't directly show up to business meetings themselves all the time. And if anybody wants to try and legally get Spiderman's secret ID, 'sorry, lawyer/client confidentiality'. And if some supervillain wants to try and beat it out of Matt Murdock... yeah, that's totally gonna end well for them. (Obviously, this applies back to the era when Matt was still practicing law, but Spidey invented web fluid before his career even started so there's still a time window of decades here.)
* Sell his inventions to Tony Stark... who, again, in a rational world should have no problem at all doing business with a guy in a mask he does not necessarily know the real name of (seeing as how he works with a collection of said folks every damn week). Collect patent fees. If necessary, collect them in the form of a briefcase full of Krugerrands.
* Get a job as Reed Richards' lab assistant. He's one of the few people in the world smart enough, again we're with the 'another superhero is understanding about secret ID issues', and he even gets the benefit of being able to tell his boss 'Sorry, I have to take the afternoon off of work, the Green Goblin is at it again'. 'No problem, Spidey, its not like I don't have to schedule my own life around random Doctor Doom attacks'. Kitty Pryde could get a regular gig as Franklin's baby-sitter back in the day, even though its a 40-mile commute for her, but Peter is Johnny's best friend and lives practically next door and can't even think to ask?
Edit: I would like to take a moment out to praise Hickman's current Fantastic Four run, where Spidey has in fact done exactly this; accepted a job at Four Freedoms Plaza. Granted, the job seems to be 'help the FF fight' as well as 'help Reed in the lab', but hey, as long as he's getting paid...
... he is getting paid, right? Huh. Well, he probably is in Hickman's book but then magically not getting paid in the Spider-Man titles, today's editing being as sloppy about continuity as they are. But I digress...
As to when Peter gets the time to do this; since he isn't actually trying to market his products himself (except in the 'work for Reed' option, but again, superhero flex-time), but is instead collecting patent licensing, he can work at home and on his own schedule. And if he has time to make the nut as a freelance photographer, well, he can quit that job and make it as a home inventor instead.
But I should be fair. This isn't Peter being unwise. This is just writer fiat. Marvel Comics has everybody magically turn stupid whenever its necessary to keep Peter poor. I damn near threw the book at the wall the first time I saw Peter going 'How do I cash my Avengers salary? Spider-Man can't cash checks!'
Seriously? Other superheroes themselves can't figure out that a guy without a public ID has a slight problem in the check-cashing line? They can't just pay Spidey in cash? It still is legal to pay people in cash at the pay window, y'know -- you just have to withhold taxes first! I'm pretty sure the Maria Stark Foundation has at least one tax accountant! *facepalm*