Realtor told me its dumb to buy a house cash or pay the mortgage early when interest rates are so low?

In an apartment right now with my wife and son. Been saving for a house. My plan is to save up 200k buy a house in the 150 range and give my wife 50k for furniture and decorations. Everyone thinks my plan is dumb and my mom is a realtor i gave her a call and she told me the interest rates on mortgages are really low right now and it would be dumb to pay it off early or buy cash. I dont understand how its dumb, somebody educate me please? Im 23yo firefighter/paramedic make 70k a year between 2 jobs

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