Concerned about an extension/add-on structure

[John Guerrero]

I am looking at a potential investment property in San Antonio, TX. This particular property has what appears to be an added-on extension to the house. There are several signs that would suggest this part of the house was not part of original structure, like the siding is completely different. 

My question is what kind of problems can this cause for me? and how do i determine if I should move forward with this property?

Thank You,

John Guerrero

PS. First Post!