In the city, it's not hard to find a spot with 2 lures going, and i'm sure you can find places with 3. Lucky eggs double the xp for any action. evolving nets 500, with the egg, 1000. You get a few lucky eggs as awards as you level. You can get around 60 evolutions while the lucky egg is active.
Level 20 is sort of the "soft max". beyond that it's very expensive to progress further. It's 210,000 total XP for level 20. 435,000 total for level 23.
Realistically, say 4 hours of catching at those lured sites buys you enough for the 60 evolutions, 60,000 xp. Let's go with 5 hours total.
Perfect conditions, i think that comes out to 35 hours. I'd say double or perhaps triple that realistically. You have to go gather loot and stuff, which still grants XP, just at a slower rate. If the OP felt like it, running the whole time with lucky eggs would cut that down quite a bit, maybe half, and cost perhaps $20. I'm guessing around 80 hours without buying anything.
A single person who's interested in it can pretty easily come up with 3 hours a day, and quite a few hours on the weekend. 30 hours seems pretty accessible. it's been out for 2 weeks or so now, so the OP is only a little on the high side. Perhaps not at all if they'd spent money on eggs.
Of course, different people have different commitments. In a rural area, this would be impossible. Family, hobbies, a long commute would drastically reduce the time available. But if your hobby is video games, it's pretty easy to swap one for another with little effort.