Location, location, location. Location is absolutely imperative for this type of business model. Your expenses will ALWAYS be more than a promoter discloses. Occupancy rate of 70% is extremely aggressive, although not impossible to achieve. The hotel industry occupancy rate is approximately 65% and hostel occupancy rates are somewhat lower. Initial costs can be all over the place, so any particular dollar investment could make sense. What you get for your money is what counts.
There is also a need to maintain the quality of the property. Having a class A property takes significant time and effort to maintain. A couple of negligent occupants could cause significant damage and require repairs. Maintenance and cleaning costs can significantly vary based upon how a particular guest treats the unit.
Research your demographics and determine exactly WHO your market is and what you can expect from them. This is a tough business and needs to be micromanaged. However, someone with a good head and a lot of energy can certainly make it work.