How Can You Assume Mortgage When Buying a Property?

[Bob Asad]

Can you assume a mortgage on a conventional or FHA loan?

For example, the house is listed for $500k and it has $300k in mortgage left at 3%

Could I offer $500k and "assume" the mortgage of the seller?

So in conclusion, it would be financed as a conventional with 20% down ($100k), and out of the $400k, $300k will be at 3% and the remaining $100k will be at the current mortgage rate?

Does anyone know how it works and best practices?