How much clearance do we need for side-loading garage
16 feet would probably be enough clearance to get a single sedan-type car into a two-car garage, assuming no other car in the driveway. I've got about 18 feet of space to maneuver into my garage, and it's tough when there's another vehicle parked in the driveway. Not impossible for my little Mazda 3, but it's not happening with our SUV unless we drive on the grass. Parking in the garage when there's another vehicle already in it is tough as well, but easier than when the other vehicle is in the driveway. And if there's a vehicle in the garage and one in the driveway, forget it - I'm not getting into the garage in that case, even with my small car.

I have trouble with 18 feet of clearance, so 16 will be even worse. If you can provide some additional space to either side of the garage door - especially the far side away from the road - that would help quite a bit. If you can give yourself more than 16' of space between the garage and the property line, that'd help immensely more.

As @Ecnerwal mentioned, this could affect resale value; it would quite severely limit the types of vehicles that could be parked in the garage, or it would turn a 2-car garage into a 1-car garage.