I think that it is a mistake to sell your property and invest in crypto now, because no one knows what will happen next, and it is necessary to live in your own apartment, not on the street and drive a car. The golden rule of investing-invest as much as it will not be fatal to lose.
Its the risk, that every investors are will to take. Its not a mistake I think, he just believe in this technology and I know thats the best decision because car is not that important and its cannot be consider as an asset as its value depreciate over time.
ETH is a good coin to invest for, but for sure you are holding huge money by selling the car of your girlfriend so for me, you must not invest that money in only one coin, try to diversify it and have more source of income.