I’m trying to get my moms house put in my name. If I buy it cheap , would I have to pay a gift tax ?i don’t know much about doing this .

The giver of a gift may have a gift tax reporting requirement. This depends on the amount gifted and other facts and circumstances. The receiver does not have to pay gift tax. To learn more about gift tax, click here.

This is a situation where you and your mother may want to consult with an attorney to ensure that the transfer is done correctly and all filing requirements are met. 

@hospital86 , agreeing with @GiseleD   but adding  a little:

(a) assuming that your mother is alive  AND   (1) that there is no mortgage on the property ; (2) that there are no other inheritors;  (3) your mother has no wills / codicils etc. in place;  (4) your mother is  willing, able  ( mentally and physically ) and under no duress to do this transfer ; (5) the property is in her name only ( or she has POA from other owner ) then this is possible.  

(b) the difference between  Fair Market Value and  what you pay for this property would be regarded as a gift by her  , and if beyond the  free limit for the year  then she will have to file a form 706 to record her gift ( against her lifetime free amount )

(c) Your basis in the property  ( to be  considered when you sell the property down the line ) is that of the donor on the date of donation --- it is  often better to  transfer the property as inheritance  ( because then the  your basis would be the  fair-market -Value  at time of death of the decedent.

I hope this gives a fuller picture of the situation