Do we have enough in-house maintenance people?

I coordinate maintenance for a property management company in Los Angeles.  We have a total of 1,576 units and I am pretty much forced to use our in-house maintenance staff for about 75% of our requests.    

The problem is that we only have three men in our in-house maintenance staff to service all 1,576 units, and many tenants frequently wait days, weeks, or even longer to get service.  I strongly believe that this is not working.

For an operation this size, how many in-house staff should we have if I am forced to give most of our requests to them?

Thank you very much for your input!  I really appreciate it!