大房的贷款可以抵一些小房的房租税收吗?
No.
我应该怎样操作才会收入最大化?
You should have take out loans in the old house as primary residence before you moved, and buy the new house with more cash. That way the loan rate on the primary residence is the cheapest.
Now you can only cash-out refi the old house, but the loan terms are more expensive since now it is a rental. But still it is better than not having a loan.
WIth the cash out of the rental home, you can put the cash in the primary home mortgage, or GO OUT AND BUY A SECOND RENTAL!