Why pay off those low-interest rate loans quicker than you need to?

Try to find a lender who will help with the cost of rehab, so you can hire some crews and turn the property quicker. 

Flips seem to make the most sense for quicker income and cash generation and can turn into a rental if they don't sell quick enough, I know multi family can be great for longer term wealth creation though...

There was also a blog written about it this week by a very wise investor;) that's a quicker read (it's here). 

As someone above mentioned, its your money, and for me, it was quicker than tapping into other sources of funds I have.

By doing this, it will allow you to acquire your next property quicker because your DTI ratio shouldn't be affected. 

That most likely will mean little to no money down on the refi.Since you have put much less of your own money into the deal, you can do more deals quicker than saving up a down payment for each property.Mind you, this only works with HML if the property needs rehab to increase the value.

If you were going to rehab a house, but got it at a good price, it might be quicker to just sell it As-Is to another investor and make your profits.Other times, people just change their minds and then try to sell it right away.

For the financially disciplined, they can help you pay off your property quicker, thus reducing the overall interest you pay.

This can help you scale much quicker.