My gut answer is that you should have no problem full timing on 50k a year. Is that 50k before or after taxes? Also, are you going to buy the coach outright or have payments? I'm guessing that it is just the two of you.
Although I am not a huge fan of extended warranties, (like Executive mentioned) if you purchase a good one, it can be a way of making repairs a consistent and budget-able item. The odds are usually against a catastrophic breakdown but one on a DP could really mess with your yearly budget and full timing ability for that year.