[Closed] Step though second hand bike. 20" wheel?

Hi,
My Dad would like a new (to him) bike, he has never been a "cyclist" but cycled a little over the years and is general quite fit for his age but finds his old bike (1980s Peugeot mtb) hard to get his leg over. I think an electric bike would be good as it would allow him to make it to his club he goes to 5 miles away. What am I looking for? I'm looking second hand so facebook and ebay. Loads of the step though ones are 20" wheels. Are these unstable? They look less heavy and unwieldy than the 700c and 26" version.

Any thoughts ideas, suggestions, budget ideas.

Or should I consider buying a normal bike and doing a conversion? (I can wheel build)

Edit: He has ridden a motorcycle all be it a long time ago so has ridden heavy two wheel machines.