Is it possible to refinance 1st & 2nd mortgages for a brand new house immediately after I close?

I am required to use my builder's mortgage company b/c they are giving me incentives but the rates are 0.5% higher than other lendes on both the 1st and 2nd mortgages. I am wondering if I would be able to refinance both mortgages immediately after I close? What do I need to consider? What questions do I... show more I am required to use my builder's mortgage company b/c they are giving me incentives but the rates are 0.5% higher than other lendes on both the 1st and 2nd mortgages.

I am wondering if I would be able to refinance both mortgages immediately after I close? What do I need to consider? What questions do I need to ask?

Sale Price: $960k
New House in California
Interest Rates for 1st/2nd mortgages: 6.75%/8.675%
Excellent FICO scores - high 700s to low 800s
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