Thanks Perna. I understand what you're saying. The thought that came to my mind at that time was that since my mom asked me to help, she sort of gave me her Power of Attorney to "speak" for her.
My mom does have trouble asserting herself. Last time she signed the papers under pressure from him, and suffered from massive stress and still does till today because of that. She kept telling herself she shouldn't have done it.

I didn't want her to get stressed out AGAIN. Eventhough its her matter, when she stresses and comes to me, I get stressed because there's not much i can do, also if she talks to me and i give her suggestions, she flips out and gets angry at me I get stressed more.

another thing, I am confused about boundries. Isn't it that if someone is rude to you, you should speak up? Or perhaps I was the one being "rude" first since its his business? But then my mom asked me to help so wouldn't I be as involved as part of it?

I guess my question is more like WHEN do i set boundries? and HOW do i set them without looking aggressive?

He told me to shut up when I didn't even say anything. I was trying to speak for my mom and tell him that she feels very stressed and is uncomfortable doing this. and thats when he said You shut up.