I say nay
You really need to cap the debt... allowing the player to borrow as much as they want means they can bet stupid amounts at the start of the game... unlock all the prizes without even racing... with giving the player essentially an infinite amount of money you really give them house advantage... with careful doubling up on a two horse match you can essentially make as much money as you want through maths.
To me this spoils the fun of the game.
I found the gambling controls kinda irritating to use... would have prefferred an odds based system, perhaps.
I quite liked the graphics... no complaints there... overall could be a good game if you sorted out the money system (which is essential to a game like this) and perhaps included more stuff to buy, the possibility of sponsoring a horse (and making more money on it when it wins) giving the horses personality (which would work well in an odds system e.g. have the steady horse that often wins but with bad odds, the tempermental horse that sometimes does amazingly well sometimes awfully, the old horse that almost always loses but has great odds).