The frames are not welded to each other. Hose clamps hold the head tube of the rear bike to the seat post of the front and the rear stays are bolted through the down tube of the rear bike. Just in front of the 2nd crankset.
I have access to a sweet triphase stick welder now and can use it at will. But as long as the clamps keep yhis one together that is all it needs.
The real spending comes slowly, the entire front wheel needs replaced, axle to tire. Both crank bearing sets are shot and the rear wheel was made of two wrecked coaster brake hubs and two ruined rims. But it was near free! I paid two bucks for a used rear tire.