Immigration Question?

I have a hypothetical question, asking on behalf of two friends...

One friend is a US born citizen, but not qualified to be a sponsor because they live in a small apartment and have a very tiny income. So, as a sponsor, they don't have financial means to support an invited immigrant, nor the room to house them. Now, if the immigrant has their own sufficient money to cover own apartment/housing, purchase a car, afford all insurance (car & medical), pay for all other expenses...like food & clothing...is it necessary that the sponsor still show a means to support the immigrant?

Next question: If an immigrant's 'invitee' were of unqualified financial status, then what is the best way to apply for immigration, and under what particular status for the lack of a sponsor? What type of visa or form should be filed? The immigrant would be a single male, mid 20's, looking for citizenship opportunity. The diversity lottery may not be an option for this person, as it's already closed for 2014 year, and only 55,000 are issued per year. The immigrant's home country will likely not fall into their guidelines for the diversity lottery anyway.

I can't help with their situation...I too wouldn't qualify as a sponsor, for many of the same reasons. The immigrant is not related to anyone in the US, nor is dating/engaged/married to a US citizen.

So, in regards to all the info, what is the best visa to apply for? And where do you begin the process or how?