Many thanks baikal3 and BigJoe5 with your responses, this is certainly helpful. I will consult with a lawyer soon. So it seems that my parents wont be able to travel outside the US until their status actually gets approved as permanent residents. In your opinion, how much time are we looking at on a best case scenario that their status will be approved? Am I looking at months or years from the time we submit my petition?
BigJoe5, both my parents came to US legally with tourist visas (and can prove it) they do not have J-1 statuses. They originally came to the US with the intention of only visiting and vacation, it was then after a few months later during their stay that they decided to stay illegally for a chance of a better life. Knowking this, does it mean its a better situation for us or harder?
There are too many unknown variables to predict how much time it'd take.
Under the very best scenario, if your parents prepare ALL the necessary supported documents, from the time I-130+I485s are submitted, it'd take months, not years, to the final approval.
However, getting all the documents together may take quite a while.
First, you need to sort out the I-864 affidavit of support situation. This may be the biggest practical hurdle to overcome.
Then there are the various necessary documents (particularly for I-485) regarding you and your parents: their birth certificates, proof of relationship to you, copies of their old passports and I-94s with initial admission stamps and visas, etc.
Also, they'll need to do a medical exam/immunization form, I-693. For many people that can take months to prepare because it requires (or at least required - you'd have to check the current rules) a medical exam at a USCIS approved doctor, TB tests, blood tests, proof of various vaccinations etc. For me, for example, getting proof of various necessary vaccinations was very difficult and I had to actually get some vaccinations here (some of them required several doses and at least a couple of months apart between those). Then there is the TB test. In many countries (such as Russia, where I am from) they used to give all kids live TB vaccines. That means that you typically will always get a positive TB reaction to a TB skin test for the rest of your life - and some USCIS doctors require a course of antibiotics to be taken in such cases, which again can take several months (I was lucky that the doctor doing my I-693 did not require a course of antibiotics, but I heard quite a few stories where this was required).
Then, presumably, they'll need some sort of current proof of identity, particularly for doing the biometrics. Do they have current valid national passports? Valid U.S. drivers' licenses?
There are also a bunch of translations to prepare (birth certificates etc), supporting forms to fill (e.g. G-325A), etc.
Also the application fees will be considerable. At a minimum you are looking at about $1700 per each parent ($420 for I-130, $985 for I-485, $380 for I-765), plus possible lawyer fees etc.
Basically the earlier you get started the better in terms of preparing the supporting documents.
Your parents are lucky that they entered on valid visas and then overstayed, rather then entered illegally. In the latter case they would not be able to adjust status, even in the immediate relative category.
