How do I file I-130 and I-485 for my parents who are on a visitor's visa?

They can apply but it is best to wait until they have been in the US for at least 90 days since their last entry so that it does not look like misrepresentation of intent at the time of entry. Please let me know if you have any additional questions or how I can be of further assistance to you in this matter.

As a US citizen, your parents are considered immediate relatives of a US citizen and hence a visa is almost always available. So when you file an I-130 petition for your parents you can concurrently file their I-485 adjustment of status [green card] applications. With respect to timing of their I-485 applications, note the general principle that when an alien enters the US ostensibly as a tourist and thereafter files for permanent residence, the DHS may find that the aliens' initial entry as a tourist was fraudulent and hence may form the basis of a denial. There is no hard and fast rule on how to rebut the preconceived immigrant intent, but the further away in terms of the time of entry to the time of filing an adjustment application, the stronger can a case be made for lack of preconceived immigrant intent.

Adjusting status in the U.S. is faster than consular processing. Although the filing fees are higher, the difference is likely less than the price of 2 airline tickets. So, unless your parents have their own reasons to go back to their country before they might receive their green cards, adjustment of status is, probably, the road to take. Is it safe, you ask. Well Does either of your parents have any criminal history or history of violations of U.S. immigration laws, involvement with a terrorist organizations or totalitarian parties, communicable diseases? Can you show financial ability to support them so they would not become public burden? To be certain about what to expect, you would have to speak with an immigration attorney and give him/her a lot of information about your family and finances. However, if there is a problem that might stand in the way of your parents' adjustment of status, the same problem will bar their consular processing, too. If their applications for adjustment of status get denied, your parents will be asked to go home - but this is exactly what they have to do in order to submit to the consular processing. So, no matter what might happen in adjustment, I see no reasons why a consular processing might be better. Quite the opposite: if you have reason to expect any problems, it is better to face them in the U.S., where an adverse decision of an immigration officer can be appealed - while denial of an immigrant visa by a consul is final and cannot be appealed.

If you are 21 years of age or older, you can file for your parents. If they file 90 days after their arrival in the US, it will be presumed they did not enter the US with immigrant intent, but the government could prove otherwise. You should consult an immigration attorney.

When your parents applied for the non-immigrant visitor visa, they had to show the U.S. consulate that they have no "immigrant intent." So if the arrive on a visa and you file their AOS application, the USCIS may question whether the misrepresented their intent to get the non-immigrant visa. However, if a person comes on the visitor visa to visit the U.S. but later when they are in the U.S. he/she decides to stay, that is, they form the intent after arrival in the U.S., they are fine because they didn't misrepresent anything to the US govt to get any immigration benefit.

I would file in the US and just wait about 2 to 3 months after their entries before applying.

Consular processing is the indicated procedural step for them since they entered the country under non-immigrant tourist visas with "no immigrant intent" assumptions.