My elderly cat

[JazzieGirl9]

My family and I recently took in a neighbor's cat. She was coming over all the time and lack of care was evident. She had mats all over her body and cried when we cut them off. We found out from our neighbor that she is an elderly cat which is noticeable when you take a look into her mouth. All of teeth are missing apart from her Incisors on the top and bottom and her two top fangs. She is a very tiny cat weighing in at about 2-4 pounds if that, but has a very small frame. We feed her patte wet cat food a can a day half in the morning and half at night. She sometimes vomits and I have noticed a lump about the size of a golf ball on her abdomen near her pelvic area. I am not sure if she has had ver vaccines and I have scheduled an appointment with a Veterinarian, I worry that she isn't getting enough nutrients in her diet and was wondering if there was an affordable way to take care of her better and what the lump might be and why she might be vomiting.