Thank you all for the input.
My husband is just below the owner of his company, and they're good friends... so, I feel comfortable attempting this. If it doesn't work out, no harm no foul. They also have plenty of money and aren't trying to "cheapskate" it, just giving me the opportunity to gain some experience.
Initially, we were talking just 3-4 buildings... so, the expansion to 10 did catch me off guard a bit. I figure I'll know by the first day if I'm absolutely awful and they'll have time to hire someone else. I've asked for a list of all the buildings so that I can get a feel for their positioning and which time of day will be best. I know several are in San Francisco, and that's both incredibly intimidating and exciting. ha.
Weekends, for sure, and I'm definitely researching and practicing a bit on local buildings. I'm the type that likes a challenge, so I would do it for experience alone... but, they won't let me. They'll insist on paying me.
After I get the list, I think I'll have a better idea of how many days it will take and go from there. Thank you all again!