Don't think I would buy it.
"Tanks can be exchanged at any AirGas/MerriamGraves or local welding supply " That quote tells me the seller probably does not own the tanks.
More often than not, the tanks are not the property of the one possessing them, that to say most of the time the tanks are rented from a welding company and belong to them. I went to a lot of trouble to buy my own tanks (I have the mid size and fill about once a year by my usage). Every time I fill, I have the hassle of having to show my ownership (sales receipts from 15-20 years ago).
Every 5 years, (or 10 depending on the test that was done), the Oxygen tank has to be tested. that is now costing around $30. The gas supply companies are now requiring an inspection (no test) of acetylene tanks every 5 years and the last I paid was about $25.
The month and year of the "hydro" test are stamped into the steel at the neck of the tank and good for 5 years, or month, year and a star for 10 years, if it is even a tank the sell can sell.
From the photo,Looks that they are the best part but I would want a "eye on" inspection before buying.
From the photo, does not look that great, but again, I would want an in person examination.
Are the with the unit, where are they?
Sorry, but it does not look like a good deal to me. I would not do it for half that amount.