As I'm sure plenty of people here would agree it is a lot of work looking for deals on old games in the wild, not every day is a zinger either for example I went out today for about 4 hours went to 25 yardsales and only found a few meh finds for my efforts.
I keep track of the addresses I've been to before for yardsales and skip them figuring that the chances of finding older games at a repeat sale to be slimmer or go back to them if for some reason I think they may have something I'm interested in from when I was at a yardsale the previous year(s). Another thing I found that works for me is I have found games more consistently in two areas around me. I normally start out in these two areas most days aside from starting elsewhere for other reasons that over rule this (some thing advertised I'm interested in, lots of sales in another area vs very few sales in the areas I normally do better in).
Unfortunately with the influence of online selling becoming more common place every year it's harder to find deals IMO (this doesn't just apply to video games) either the price is higher or a few people I've talked already this year hinted at something video game related that was found when getting ready for their yardsale that they rounded up that they had no interest in selling (or at least at a yardsale).
Every area is different in what you can expect on an average day. I'd say if you haven't already stick with it for about a month and decide then if it's worth your time, trouble & gas money.
FWIW I don't live in the middle of nowhere but I certainly don't live in a metropolitan area. For example I remember my one friend getting the only copy of Mega Man 7 that our local Electronics Boutique got when it came out and Electronics Boutique was the only store around me that carried TG-16 stuff when it was current.