Actually, if the condo was built with today’s required insulation, a 75,000 btuh furnace is adequate for two such condo units. In other words, the furnace is twice as large as required, will either shut down after a few minutes on high limit or blow such an amount of warm air that the papers may fly around the room. The furnace would be the right size for an uninsulated concrete garage in the northern US.
The best way to find the right size appliance is to estimate the heat with a Manual J heat loss estimation procedure, which is the industry standard method of finding the right size heating unit. Obviously, the estimator of this heating unit was a Texan who uses a commercial tractor-trailer to pick up a pack of cigarettes. You can perform a free heat estimate at http://www.hydronic.net