I've been fulltiming for over 2 years with an erratic unstable income.
I can tell you right now that if I had 35K a year the past two years (70K) based on my past expenses and workamping (free rent, but no salary) I would still have 40K left in the bank. I keep meticulous records, so I know exactly what I spend. My RV is in good shape and well maintained. It's old, it's used and I love it. I spend some here and there to upgrade a few things now and then. It's a helluva lot cheaper than making payments (my little old RV is paid for).
I live very comfortably, but I have a ying and yang to enjoying a lot more with a lot less money. I've been to 17 states and oodles of campgrounds and sightseeing. I don't bother with eating out except as a rare treat, I cook up healthy foods at home. I don't get out and run around in a car every day, I don't own a car, don't tow one. It saves me a bloody fortune. I take my RV shopping and sightseeing between campground stops.
While workamping, I combine a shopping trip with sightseeing. While a car might get better MPG, I am able to take my kitchen with me and not be forced to spend money in restaurants for the day. Plus the dog gets to go everywhere with me and that is fun for both of us. Instead of worrying about 10 tires and 2 engines, I just have the one engine and 6 tires and no extra insurance and maintenance costs by having a toad.
I am not of retirement age, but who says I have to wait to have fun? I am having my fun NOW.
I do walking and photography. You see so much more walking around than racing by at 70mph.
I've been spotted shopping in used charity shops and skipping meat purchases at the grocery store. But I've had an absolute BLAST and wouldn't trade the last two years for anything. Being single I spend the same on gas and camping fees as couples, so basically if a 2nd person was with me, there would be extra food and their personal expenses (clothes, toiletries) but it certainly wouldn't be double the cost.
I've got tons of health issues and no insurance coverage. I went alternative, changed my diet to healthy, relied on herbs and exercise after doing a mountain of research. I was on 17 medicines the docs said I needed for the rest of my life and now I am down to just ONE medicine, that I wish I could get rid of and probably will find a way. I don't even see the docs anymore. They want to kill me with drugs that were hurting my kidneys and liver, besides giving me loads of side effects I did not want, now I am off those dangerous poisons. Also they aren't dipping into my bank account anymore, I am not a slave to the drugstores and doctors and I love it.
None of my workamping gigs have paid any cash, just free camping. But I am happy and loving life. One thing about living in a small RV, you don't have room to shop for junk. Even my wardrobe is efficient though year round, ready for hot or cold. Most of it was bought at used shops, some with new tags still attached even the price was way cheap. If you run into me in public in a beautiful dress, how do you know whether I got it at a used shop or paid top dollar for it? I have a compact washing machine, so I can pretty much wash as often as needed and therefore don't need a walkin closet full of clothes.
One thing is you have to always be setting aside money for RV maintenance and surprises. If you are worried about living off $35,000 a year then start keeping records of every penny spent so you can see exactly where your money is going, then you can adjust your expenses to more closely resemble your goals.
I wanted to fulltime in my RV now, not later, so I was willing to find a way to do it.
Good luck and have fun!