Purchasing a house and dont understand this plumbing

[Dmartin411]

I am purchasing this house and not dont understand this run. I am an elevator mechanic and not a plumber. They house had a bathroom in the basement but the drains are capped off. Also the stack seems to have been repaired with a pvc Y going out the side wall to what appears to be a vent? In the basement pic you can see the pvc pipe with the old pipe in the basement floor capped. What is this? Why would the disconnnect it from the floor and shoot it out the side of the basement at head height? You can also see the pipe on the outside pic with just a 90 facing down. Was this a vent going through the basement floor? House was built in 1967

 

[Breplum]

Frankly, too grainy on the photos, but, no real way to evaluate anyway. clearly the main drains go straight out, so, home inspector may have some interpretation.
Make sure there is a clean out on the other side of the wall.. an indoor clean out is nice, but a real mess if there is a clog downstream.