Comfortable high-tech subsistence farming is around the corner. Efficient local renewable energy, RepRap machines, domestic robots... it's going to be a very interesting century.
Regardless, there's a reason you seldom hear "comfortable" and "subsistence farming" in the same sentence. Growing enough food to feed yourself is a full-time job, even with modern agricultural tech. Yeah, there could be a singularity-style event that makes traditional farming obsolete, but RepRaps and Roombas ain't it.