It will definitely boost your returns and in 30 years you will own a bunch of properties free and clear. 

Plus its not that easy.. the business has to qualify and real estate generally does NOT.. not enough employees  I looked at this heavy about 10 years ago.. unless the regs have changed dramatically.. it was a non starter for developers of real estate.

If vacancy or delinquency by a couple tenants will dramatically impact your returns, you're exposed. 

Cap ex can change dramatically depending on the age of the house. 

Are they just saying this to sound dramatic and look cool because everyone is going to be like "oof, this guy knows what's up" ? 

Get those CCs paid down, and you'll also potentially earn higher credit limits on those existing cards (a good rule of thumb is to keep your utilization lower than 30% of your limit which, if done consistently, can boost your credit score). 

painting and carpet might not give you enough of a boost, needs more detailsHave you already bought it or are you projectingYou can add value by increasing rents, improving the property, refi, adding sq footage etc.

Ditch the ugly old ones and look for stylish new oversized mirrors to create the feel of dramatically larger spaces and more light.

I wanted to add to the list of ways that you can boost your credit score! 

Each of these variables will dramatically change the advice I give the individual asking me this question.