If you are in Philly, Spring Mountain is close. I started last year (living 10 mins away from Spring Mt.), I am 45 and not very athletic anymore. I took a group lesson to get started then every day I got a private lesson, two trip to the slope a week was as much as I could handle. Way fast way of learning. Starting in mid-January by the end of February I was able to ski in control every slope at Spring Mountain and Bear Creek.
So equipment, I bought boots after the first day, googles and helmet two weeks later, having your own boots is great. This year will be a pair of used skis or season rental and cheap poles preseason. For clothes I grabbed an insulated work bib by walls at Walmart and sprayed it down with water proofing spray. I had a jacket, and bought several pair of gloves at the slope during the year. By the way, nothing cheap about this hobby, but your sister can explain that to you.