However, I specialize in lease-to-owns (or rent-to-owns, or lease-options, or lease-purchases) and I've never heard of a "land loan" or a "lease loan." In different parts of the country, similar structures may be called "contract for deed." (There are differences; see: http://www.creonline.com/articles/art-196.html ).
All of these involve making payments to the owner and, at some point in the process, receiving the deed to the property.
There's also a similar way to accomplish the same end result using a land trust.
However, I have never heard of either a "land loan" or a "lease loan."
As far as getting grants, no. There aren't grants, in the usual sense, for homebuyers. There are a number of first-time purchaser programs. Some are promoted by lenders. In other cases, cities or counties will sponsor them. But they aren't grants.
Similarly there are a number of programs--AmeriDream and Nehemiah--that are down payment assistance programs. AmeriDream is at http://www.ameridream.org/ Nehemiah is at http://www.nehemiahcorp.org/ But there not grants.
If you want to buy conventionally (getting a mortgage up front), talk to a good mortgage broker to find out what programs you might qualify for. If you want to do a lease-option, that's fine, too.
Hope that helps.