Strength training for Caregiver?

I need to get really strong in the next few months to help out my sister who has lost the use of her legs. She's in a wheelchair and needs assistance getting moved (in and out of her chair, to bed, the bathroom, etc.). Fortunately I'm not by any means her primary caregiver, but I'd really like to be more useful if I could be. The way she is able to be moved now is by facing her and lifting her up to a standing position, pivoting her and setting her back down where she needs to go. Like bending down to hug her, than lifting her up while she hangs on to to my neck. I'm guessing I need to get strong in my arms, back, and legs. I am a bit taller than her, and she weighs a bit more than me. I can lift her up now, but it's hard, and will get harder as her disease progresses (she has ALS) and she is unable to lock her knees. I'm small boned, thin, tall, mid-30's if that helps. I am not able to join at gym at this time or have access to a home gym. I could spend some money if it would really. Any advice would be really appreciated. Thanks for reading!