When I start with a new character, I grind up to $130. Then I buy a Bionic Arm from the secret shop in the frist level, which raises strength by 50. Then I grind money to pay off Scott's late fee's. Then I fully upgrade my character. Takes some time, but it's faster than doing it normally.  
 
Anyone else doing something different?

I just go straight for the late fees.

Surely it takes more time to grind for the late fees than to actually finish the game.

I haven't tried it, but apparently there's an exploit where you can load up in co op with the second player on a guest account and transfer money to another character in the shop (press circle). When you save it remembers your main account got money but forgets your guest gave it away. So you could just do that once you get a lot of money and skip most of the grind...

I do this too! I always think trying to go straight to the late fees might be worth it, but getting the Bionic arm makes the grinding process just go a hell of a lot faster. I tend to get up to Level 4 and then just grind 1-3 till I get enough coins to pay off the late fees and fully boost my stats, too. 
 
Gotta finish my Kim runthrough today, then I can start a Ramona one and unlock NegaScott. God, I love this game =D

With a new character, I just bought CDs as I got money.  It's by far the fastest way to level up your character and make progress in the game at the same time.

" I haven't tried it, but apparently there's an exploit where you can load up in co op with the second player on a guest account and transfer money to another character in the shop (press circle). When you save it remembers your main account got money but forgets your guest gave it away. So you could just do that once you get a lot of money and skip most of the grind... "

" Surely it takes more time to grind for the late fees than to actually finish the game. "

My brother's and I pooled our cash together to pay off Scott's fees faster and got maxed pretty quick. We only really had to grind for the Todd battle, everything past, while occasionally challenging, wasn't impossible.

I use the strategy of not buying the game.

i just ate the 8 dollar sushi for +1 to all stats.it takes awhile but eh it works (for me).

I paid off the fees and sunk my teeth into the cheap 1ups, while constantly buying the videos they had available.

I actually never tried to pay off the late fees on my first go through.  I spent my money on food and clothing items as I went along, and didn't start buying CDs and games until I had reached about stage 5 or 6.  Over time, some of my stats were just insane, but my strength score tended to suffer and I never bought any extra lives.  I fought through the last section of stage 7 by the skin of my teeth.

I've been going for the bionic arm first too. Then I just grind and go back to wallace's shop for the final fantasy and sonic upgrades until i'm at 100%. Maybe not entirely cost effective, but the late fees feels like a lot to do all at once. I like to get upgrades asap.

This Game is Sweet

I thought you meant the fighting strategy where you knock someone down, pick them up, throw them, light dash attack them as they're down and then quickly pick them up again before repeating until they flicker away.