Final answer:
The maximum security deposit Michael can charge is dependent on the local rental regulations, which may include limits set by rent control laws.
Step-by-step explanation:
The maximum amount that Michael can charge as a security deposit for his apartment building highly depends on local rental regulations.
These regulations can vary significantly from one jurisdiction to another, as they are often established by local laws or housing codes. With this in mind, without specific information on the locality's regulations, options A) $600, B) $900, and C) $1,000 cannot be accurately determined.
However, it's crucial to note that if a city has passed a rent control law, such as the hypothetical situation resulting in a demand-exceeding supply, this will also impact rental ceilings and could extend to include security deposit limits.