Hi Sue,
I think the waiting time for a Non Contributory Visa is 20 years, but by my understanding the 173 is a temporary one, then you have to apply after 2years for a permanent one The 143 Contributory one you can apply for, but you have to get someone to sponsor you by filling in form 40 it's called an AOS assurance of support. Both require quite a lot of money.Not sure how the temporary one would work though cause after 2 yrs you would be 65 when you can apply for an Aged Parent one.
Hope that helps
Heather