Are you sure you saw multi-family properties for $80,000 with a gross monthly income of $1,700 on our MLS?
If in fact, there were multi-family properties out there you can purchase for $80,000, with a gross monthly income of $1,700 and ready to rent, meaning no repairs needed, you will be facing fierce competition.
I don't mean to disappoint you, but I am active in this forum to provide Buyers and Sellers with the facts rather than just adding another "client" to my list.
Realistically speaking you may purchase a $110,000 duplex with a monthly gross income of $1,200 - $1,400, then again, there will be dozens of cash Buyers interested in a property with such return.
Regarding property taxes, assessments vary depending on the location, our County is divided into Unincorporated Miami Dade and a number of municipalities and villages.
Cost of insurance also depends on many factors, age of the property, electrical, plumbing, roof and water heater updates (aka 4 point inspection), location, etc and it is something you will need to quote individually with an insurance agent every time you consider the purchase of a property.
All your questions are valid and very important, however there are too many variables to determine just one answer. Property taxes depend on the property location, size etc so it's hard to estimate based on the price only. Same with insurance, it depends on the property type, condition, does it have hurricane proof door, shutters, alarm, etc there are many factors influencing the quote. Average insurance on the single family home is around 2-3k if the property meets the criteria. Rental income will depend on the purchasing price and then again location, the better location and property condition, the more you charge and the higher the ROI.
I will contact you directly to provide more details.