Depends on how good you want it to look and how long you want it to last. Like any other kind of refinishing, the condition of the surface being done will determine on how long the finish will last.
Yikes, that is a painted gunite pool, it needs all the paint stripped off and then prepped for new plaster. Additionally it should have a tile line added at the top. I suspect there is structural issues as well with a pool that old. Fixing it right will likely cost somewhere between 25-35k.
That pool needs a water blaster rental and some bond kote sprayed on it. Do the tile and coping stones at the same time. Might as well tile the edge of the steps. Time for new marcite/plaster
sigh....I thought it was really time to basically redo the thing. there is a crack that starts from the pool deck that goes down the center of the pool wall. it doesn't leak (since it was patched when we painted last year) but i did have to re-patch it during the summer. I had someone come look at making a vinyl liner for it last year, but they said they believe it's actually a old school 1960's concrete pool done by hand and not gunite. with only one skimmer and the placement of the one return, and no drain, the water circulation isn't great. so I would want to address that. the pool doesn't stay clean for very long, and well as alluded after putting on the solar cover and coming back from vacation, algae started to grow, hence the staining which i couldn't see the pool is definitely not a priority, but if we do it, I would want to do it right. The water is too cold with not enough sun during the day, that no one wants to use it without a heater. also, the decking needs to be redone, the coping, etc. so i think the best bet for now is to clean up the dirt, close it pretty much indefinitely until it can be redone properly. without doing any research, i think it's about $50k in all. So what color cover should i choose for the next 5 years?
You can DIY a solar heating coil out of some wood, plexiglass, spraypaint and pex for fairly short money.