Can i just fill out the necessary paperwork when i'm there?
Yes. It'll be nearly impossible to get a visa (I'm not sure if it's actually disallowed, but I can't imagine them granting it when you can just apply for the Karta Pobytu when in Poland) in advance - mainly because most employers won't hire someone from outside.
The Karta pobytu allows you to work?
No. You will have to be in possession of a work permit (strictly speaking, the employer applies for it on your behalf) before you start working. Do not, under any circumstance, work without it - if you do, the punishment is an automatic year ban from Schengen.
I don't want to give away too many personal details but i would be helping them around the house and also in their little shop they own.
Won't help at all. The Foreigners Office couldn't care less what you're doing in your own time - you still need that valid, acceptable reason - and helping a family out isn't it.
In addition i'll have around 30,000 zł (about $10,000) i think the rate is 100zł a day or something? But it doesn't seem like money is a big factor.
That won't be enough to make them grant residency on the basis of having enough cash.
You need to come to Poland, find a job, get a work permit and then apply for residency. You've got 45 days to do this.