We have a 50 that was changed out before we bought there is just 2 of us. Last I saw was high efficiency needed a SS liner. Unless you go electric point of use but then no power no hot water. Unless you have a generator.
Water heaters are a PITA last one waited till I left for work before it decided to leak out the bottom. It was cheaper to get someone to change it out than to lose the day. Crawl spaces suck.