That one looks pretty stout ! How is the speed controlled ? Electronic, belts, gears ? How is the column attached to the base ?
Find someone who is a machinist who can "tram" the X, Y and Z dimensions. It is not that difficult. You need a machinist share and one maybe two dial indicators. It won't be prefect, but you will know what you are buying.
Tram is squareness of the spindle to the table. On a bigger machine (thinking Bridgeport & friends) there are specific mechanisms built-in to adjust the head/spindle in 2 dimensions. On this one its scraped into the Z-way column alignment. So there is no changing it on this machine short of busting out your surface plate and scraper which is a job fraught with extreme peril.
You need 1 dial indicator and a bar bent in an L- shape to "tram the head". It can be something you bent in a vise with a hammer as long as it holds the indicator rigidly. The bar is put in the collet & tightened and the spindle rotated slowly by hand, observing the indicator marks. One can either "jump" the table slots or use a 1-2-3 block with no-holes. Note readings at 12:00, 3:00, 6:00 and 9:00 and the changes are made (where possible) to make all of those readings equal.
Now your head is in tram and its time to indicate the fixed jaw on the milling vise....
Personally I'd say as long as there isn't extreme backlash in the X or Y leadscrews its going to be OK. I'd want to cut a little metal if the seller is willing for a live fire test. In my book, having a Z-way is much much better than a round column.