I used to work at a coop bike shop and as surprising as it might sound, I had to build a few dandy horses for adults over 40yo, not knowing how to bike or swim is sort of common where I live. They were all very happy with their cheap 5-10€ bike with 650A wheels and pegs instead of the BB/crankset. This would let them commute to work feeling secured on the bike, not scared of crashing. They'd usually come back a few weeks later, once they were confident with bicycles, to exchange the fake bike for a proper one.