To increase the value of a rental property you must make sure that the property is in the best shape it could possibly be. You also need to be informed of the fair rental market value, often Landlords renew the leases or lease the property below market, that is why a Landlord should always use the services of a Real Estate Professional.
Have the rental value of the triplex increased?
Certainly, rental values have increased in all sections of Miami Dade County.
Income often is primarily rental income, but not always. Look for other areas to generate income. Washers or dryers (paid), for instance. Or if there's a separate garage on the property, rent that out.
Reducing expenses is self-explanatory, but... You don't want to reduce your expenses and have your income reduced, too. For instance, it might make sense to spend a bit more, upgrade the property a bit, and collect more money from rent. You want to reduce expenses by becoming more efficient or spending your money more wisely.
On one rental property I have, we recently spent a lot of money upgrading it--granite countertops, stainless steel appliances, etc. But we were able to increase the monthly rent by $800. That investment will pay for itself in about 5 years--which works out to a 20% ROI.
So: Increase your net income.
Hope that helps.
Jenny Arias May