@JohnD @Wade
About "May kotse ako" and "Wala akong kotse". You'd notice that in the negative, "ako" became "akong". That's because "may" is used only as the abbreviated "mayroon". With "mayroon" and "wala" they become:
Mayroon akoNG kotse. = I have a car.
Wala akoNG kotse. = I don't have a car.
Why is there a "ng" at the end of "ako" or any other pronoun for that matter? It's because "mayroon" and "wala" function as modifiers when used with another word. Without the pronoun, those two sentences become:
Mayroon NA kotse. = MayrooNG kotse. = Has/There is a car.
Wala NA kotse. = WalaNG kotse. = No/There is no car.
The "ng" gets attached the pronoun instead should a pronoun come between the two words.
Mayroon ako NA kotse. = Mayroon akoNG kotse.
Wala ako NA kotse. = Wala akoNG kotse.
When "may" is used in place of "mayroon", we don't use a "na".
May kotse ako. = I have a car.
May kotse. = Has/There is a car.
You can't use "may" immediately before a pronoun though and neither can it stand alone. "May ako kotse" would be incorrect. And should you be asked if you have a car, and if you do, you may answer "Mayroon" (I have), but you can't say "May".