For those with a skeptical nature, I hunted down these numbers.
HUD does not provide numbers to "end homelessness", they report on the state of homelessness including an estimated census of the homeless.
Some annalists have taken these numbers and multiplied them by the cost to imprison someone, or the average cost of American housing. These estimates come out to $11-30B.
So the numbers check out. The only fault I could find with this meme's claims is that they are slightly misleading in suggesting $20B could "end homelessness" without the caveat that that's only for one year.