For all of you who missed this, in 1873 Congress has already ruled on the issue of impeachment for crimes committed before taking office. They ruled that crimes committed before taking office were not impeachable events
Link
The Strong Argument That Trump’s Involvement in Payments is Not Impeachable Offense
https://lawandcrime.com/legal-analysis/can-trump-be-impeached-for-payments/
https://books.google.com/books?id=gA3enzqt4I4C&pg=PA27&lpg=PA27&dq=1873+impeachment+vice+president+colfax&source=bl&ots=nQe88mX5aQ&sig=FpEiSnnk1Sp6YJVggDsHODzNOsA&hl=en&sa=X&ved=0ahUKEwiE1byn-4rQAhVJyFQKHfB4ADEQ6AEILjAD#v=onepage&q=colfax&f=false