如果他妈妈给他钱他就可以买车用IF就虚拟

两句都可以的

第一句是肯定句，如果他妈给他钱，他就买车

第二句是否定句（虚拟语气），除非他妈给他钱，他才会买车(同时还有潜台词，事实上，他妈不会给他钱的)。

所以，英语的时态和语态很重要。
比如：
If you win this game, I will... 这是给他加油
If you won this game, I would...这是打赌他赢不了

Come on, both of them are acceptable.
In the first sentence, you use "is" AND "will". First conditions.
In the second sentence, you use "WAS" and "would". Second conditions.

The diffence between them is that the first sentence is more possible than the second.

IF HE WERE GIVEN MONEY BY HIS MOTHER,HE WOULD AFFORD A CAR.