"The money that would otherwise go into a second vehicle"
I don't think you're going to like the math very much.
700 miles divided by 4 mph which is real slow for a bike (maybe up a hill?) or real fast for a walker, times maybe $100/hr as a consultant, equals about $17500/yr or about $1450 per month. You can rent a decent new Porsche 911 for about one grand per month as per leasetrader, so ... More realistically selections of vehicle and billable rate scale hand in hand. Or if you like a cost basis, my cost per mile has averaged under fifty cents per mile for my car so you're talking about around a buck per day, which buys like one organic apple around here. Which is better for you than no organic apples. I'm just saying the extra food probably isn't enough to fatten you up.
Note I walk about most nights after dinner and also after lunch. For health, and fun. Have to be realistic that neither of us are saving any money doing so. Long term medical bills, maybe.