I'll add my two cents to what's been said. First, it is a very confusing process. The requirements vary by state, so you'll need to do research. Contact your area Medicaid office for an application and instruction book.
The limitations have to do with total monthly income from all sources - Social Security, pensions, annuities - must be below a certain amount. Liquid assets (cash) must be below a certain amount - you have to supply all checking and savings account numbers and statements for so many months back. He is allowed a certain amount of insurance for burial and final expenses. If his spouse is living, she can keep the house, otherwise he should own no real property. He can keep a car for personal use. If he has any other investments, whether property, stocks, art, jewelry, etc. those have to be liquidated before he would be eligible. Basically, he has to spend down his entire estate and be nearly destitute before he can qualify. There are exceptions and work arounds, which is what the lawyer should be helping you do. I don't know how it works if he is staying home, rather than to a LTC facility, but his medical expenses probably need to far exceed his income.
I'm about ready for a nervous breakdown trying to wade through all the requirements, myself. My mother has been in a nursing home since April, and I still have all these hoops to jump through before she will be accepted. I almost got into a shouting match with someone at the VA about her change of status.
Also, if you haven't done it already, get a *financial* power of attorney for your dad before he gets unable to sign. Every time I turn around someone wants Mom's signature with witnesses.
On the topic of siblings. Mine are generally supportive, but one brother sent a message to the NH which wound up in the home office. He wanted info about our mother's care, but he is not a designated contact. Her medical POA designates me as primary and our other brother as secondary. I'm pretty sure his motives are honorable, though.
Well, I gotta go. Hope everything goes well with you.