If you have stable 500w from solar panels you still need a bigger power supply at least a 750W i personally would still opt for eth mining with some powerful gpu
yes but will this be long term? in August there will be merge of ETH 1.0 and ETH 2.0 to ETH 3.0
Do not buy expensive video cards now, because you will not be able to recoup them and prices are constantly falling. It's better to buy a cheap graphics card like a Rx 470 if you want to try mining. But now is not the best time to invest in mining.