Arbitraging High Mortgage Rate with High Rate CD

[Carlos Ptriawan]

As the financial market is still at inflection, I found something unique where we can arbitrage the mortgage payment with high rate CD, I know it's temporary but still pretty cool. 
For example, the lowest rate for 30YFRM I've seen is 5.25-5.5 , so lets say the monthly payment is $560 for a loan of 100k.
Now the highest CD/MM/saving is approaching 5%, for 100k CD I could make $5,000.

So I could pay 70%-80% of the yearly mortgage "for free" by investing at CD.
Now if home market is rebound, actually my money appreciation would be doubled as equity building is moving up without actual cost from me :)

I dont remember if I can do something like this during low-interest rate era. Is my calc. off ?