CorvusCorax
'It's only a laugh, no harm done'
I probably didn’t clarify I meant like paying every day cost for a few months, getting new equipment, vet visits. Imagine spending years paying for everything and then to have a give the dog back to the original owner as dog are expensive you could be down thousands. Yeah the last dog I bought was 2012 still going strong and acting like a 4 year old probably not the best breed dog as he was a cross breed. The adoption fee isn’t actually bad.
If expense is such an important factor, rather than the emotional impact of having to give a dog back, maybe wait until you have a bit more money behind you, before getting another dog?
The previous owners would need legal proof of ownership to reclaim the dog, like the microchip being registered to them, pedigree or registration where applicable (also tied to microchip) or registered to a vet. Why it's important to have all these things sorted and to know exactly where the dog's chip is and check it every so often in case it moves.