I believe if you read the original SEF ARI requirements they mandate maintaining your investment. Which equates to owning the real estate outright as was original purchased. Taking a mortgage would change your Registo Predial to the bank ownership so that’s really out of the question. Switching to another RE of the same or higher price would reset the start date of investment, so again, not a good prospect for renewal.
I would not recommend.
With the same caveat that I am just a random guy on internet, not knowing much about GV 