I am a young solo full-timer, on the road for 3 years now. In 2015, my cost of living was $15,693 or about $1,308 a month. Might not be as applicable to you two, but helpful for other younger folks who're looking to travel. I work-camp for a living so my travel style is several months in one place working (national parks in the summer, Amazon.com in teh fall), and then "vacation" time at the start of the new year January - April.
If you'd like more details or to see my numbers for every year I've been on the road, they're here: http://www.interstellarorchard.com/2016/01/29/2015-full-timer-cost-of-living-and-income-report/