There's an often cited figure that it would cost $20 billion to end homelessness. As best as I can find, that figure is taken from an interview in 2012 with Mark Johnson who was with the dept of housing and urban development at the time, he wasn't directly quoted in the interview, it wasn't an official statement from the department, and by his own admission it was a rough estimate, I'm also not clear if that's a global figure or specifically for the US, though I suspect it's for just the US.

The wealth of churches can be a bit hard to quantify, between cash, investments, real estate, artwork, etc. across multiple countries and various legal entities, but either organization is worth, at the low end, easily 10s of billions of dollars, and possibly hundreds (I tend to see estimates for the Mormons somewhere between $100-200 billion) and in the case of the Catholic Church, they are almost definitely sitting on some properties and artifacts that could only be valued as "priceless," if the Pope, hypothetically, decided to sell off the entirety of Vatican City, how would the value even be determined for that?

So if we assume that 20 billion estimate is good, either church could handle it pretty easily.

That figure is over a decade old at this point though and so likely outdated (if it ever was accurate at all, which is questionable at best,) I'm seeing other sources saying that the true price to end homelessness would be at least $300 billion at the low end.

Which, again, may possibly be within either or both church's ability to pay for out of pocket depending on how they use their assets, but even if it's not, they could certainly put a very good dent in the problem.

You could also quibble about what it means to end homelessness and the appropriate ways to go about doing so.

So in short, they could maybe do it, but at the very least they could certainly afford to do a lot more than they are.