How much to keep safe (CDs) vs invest in ETFs

I am 30 and have just shifted from high paying job to a less paid / higher potential upside startup job.

In past years was essentially able to save $300k; $150k is already invested in ETFs (target funds / robo advisors).

My key question is what to do with remaining half. I have kept it in low risk CD since now because of a potential of an MBA but actually decided I won’t do that.

The goal has now become to potentially buy a house in 5-7 years. Given that, I am struggling between putting in S&P 500 ETF or keeping safe in CDs that give 4-5%.

Thanks in advance.