Newbie Homestead Property Tax Question

[David Y M.]

I apologize if this is a noobie question.

I am currently looking at a property in Collin county for a primary residence with a mysteriously low tax assessed value - half of all the other houses on the block. I looked deeper into it and it seems to be a joint ownership split 50/50. Is it even possible to split a property tax base like that? I tried looking online and it doesn't seem possible, but it's the only reason I can see that would make sense.

My next question is - if it is in fact not split 50/50 is there anyway that I can dispute my newly assessed property tax in 2021? As far as I know if I apply for homestead exemption it won't be effective until the year after. 

Thanks in advance!