How does an assumable mortgage work? Seems like a great idea now!

[Scott K.]

With rates 6.5%-7%, especially for investment properties right now, I just read about assumable mortgages where you simply take over the mortgage of the seller when you buy the property. How does this work? Can anyone do it? Does it cost extra?

If the property is more expensive than the seller's mortgage, can you take out a 2nd mortgage on the home? Or are you forced to simply buy the rest in equity. I'm very curious if anyone has done this or has any suggestions.

Thanks!