You can find one of these inside Wang Autos once you have finished those mission. It can also spawn around Garcia, San Fierro, as well as near the strip and in Prickle Pine in Las Venturas, and in Vinewood in Los Santos.
It can usually be found in the Paradiso, Downtown and Doherty areas of San Fierro. If you need one for Export, you can find one next to one of the radar towers at Easter Bay International Airport in San Fierro.
The Bravura is a pretty common car that can spawn throughout the game. In the "Architectural Espionage" mission, one can be found outside of the Las Venturas City Planning Department entrance near the Come-A-Lot casino. Also, they can periodically be found inside the San Fierro police station garage.
You can find one of these in the Bayside Marina parking lot in Tierra Robada, as well as the Easter Basin Naval Station in San Fierro. They're also common around the Easter Basin docks in San Fierro.
The Cadrona can be found all over the game, but some locations include under the Mulholland Intersection in Los Santos, as well as in the parking lot of the Las Venturas Airport.
You'll have an easy time finding the Club in Las Venturas, in such places as Prickle Pine, Old Venturas Strip and The Strip. You can also find them in the wealthier areas of Los Santos and San Fierro. Note that you can get one by getting the relationship status to 50% with Millie Perkins.
The Esperanto doesn't have any locations where it is parked, but if you're driving a Sabre, Clover or Stallion, they are common around Garcia in San Fierro. Also, you might be able to find one in Los Santos, either in Ganton, Idlewood or Willowfield.
You can find one in front of The Camel's Toe, but only if you still need it for Exporting. Once you do that, you are able to import it from Easter Basin for $28,000 on Thursdays. You may also find it in Los Santo's International Airport's lower floor, or driving around Easter Bay International Airport, although it is known to be rare.
You can find one in a highway stop near Back o' Beyond in southeast Flint County if you need one for Exporting. Likewise, once you do that, you can import it from Easter Basin for $28,000 on Saturdays. If you're driving a Merit, you might find one driving around Financial in San Fierro.
The Fortune can spawn all around in the game, although you'll have more luck in urban or residential areas in the three main cities.
The Los Santos Vagos and Varrios Los Aztecas use the Hermes as their gang car. As such, you will most likely find one in Los Flores, Las Colinas, East Beach and El Corona in Los Santos.
You can usually see one driving around at The Strip in Las Venturas. Additionally, you can get a green Hustler by dating Denise Robinson and getting the relationship status to 50%, although you can push her car into one of your garages and once it closes/reopens, it will be unlocked.
The Majestic is one of the gang cars driven by the Ballas gang in Los Santos. One location where you can always find the Majestic is in the parking lot under the Mulholland Intersection in Downtown, Los Santos.
You can usually find one at the Xoomer Gas Station in Easter Basin in San Fierro, although it's locked a lot. Also, the Manana spawns a lot in Da Nang Boys territory, like Easter Basin.
The Picador can be found almost everywhere in Los Santos. One place you can always find one is in front of Ryder's house in Ganton, Los Santos, even later on in the game.
There are a few places where the Previon will spawn, most notable in Doherty and Downtown, San Fierro. There are no known locations where it is parked.
The Stallion can spawn in Doherty, Battery Point and Garcia, all areas of San Fierro, as well as San Fierro Rifa territory. Also, if you need one for Exporting, it is in front of the Burger Shot in Garcia, San Fierro; once you finish that, you can import it for $15,200 on Wednesday at Easter Basin.
The only location where you can find a parked Tampa is in Jefferson, Los Santos, at the used car lot. Otherwise, you might find it while driving around in Easter Basin and Garver Bridge, in San Fierro.
The Virgo doesn't have any known locations where you can find it parked. However, you can sometimes find it driving around Rockshore East, Las Venturas, as well as the eastern areas of Los Santos.