My advice would be to look for an elevator. I have the platform lift and I regret buying it even though I saved some money. First off they are loud and slow. It takes over a minute and a half to get to the basement. I hate how long it takes. They do have interlocks and for our house we have a normal door that locks on the first floor when the lift moves. The floor of the lift is a grate so one can see if its coming down on anything.
Also anything labeled medical or wheelchair is expensive. The elevators they have now are getting less expensive quiet and move people faster.
If and when we finish our basement I'm ripping this lift out.