Welcome to the forum, @Noemi smith
Unfortunately, you have discovered one of the biggest problems with immigrants wanting to bring over elderly parents. Affordable healthcare in America has been a concern and challenge for Americans for a number of years. I am glad you are doing your research now because we have seen horror stories of immigrants bringing over elderly parents and only then finding out that they will have to pay $1000s of dollars a month to offer them adequate health coverage.
Immigration requires a great deal of sacrifice; whether it is time, money, separation, or a combination of any of those. One of the main requires the US governments wants in order to sponsor an immigrant, is an assurance that the sponsor is capable to covering the financial burden. To put it in simple terms the government is basically saying, "You want to bring over loved ones, you have to be able to afford them." So to answer your question about help with benefits, you would be considered the initial help for your parents benefits. You can search for Affordable healthcare that fits your budget. Be warned that the more elderly and the more ailments your parents may have will increase the cost even at an "affordable" level.
Fortunately, there are options for additional help. Many states offer coverage for new immigrants, including the elderly. You will have to some more research to find assistance and subsidization programs. Many are be based on your state residence. For example, Medi-Cal is a subsidized program that offers medical assistance to low income and disadvantaged individuals and families. Immigrants are eligible.
If you provide the state your family will be living in there may be some members who are aware of support programs.
Best of luck.