As with any real life park, the rides are free, and the guests are only charged when entering the park through the gates. They're also able to purchase things, including food, drinks, sweets and souvenirs. In the game, there are no games and stands available for them to try their luck into winning prizes (at least not in the vanilla content), and there's also no arcade rooms for them to toss a buck or two.
While it seems quite phony and academical, it's true, and leads you to understand that your main source of income in these parks, are the shops and stalls. New players have a tendency to fail in building enough stalls/shops to satisfy their guests, resulting in a massive income loss which often ends up being critical when trying to reach their objective.
Like many other "real life" parks in the game, this one is blatantly lacking in shops and stalls. You should begin by adding more, spreading them evenly among the park. This park is small enough that it doesn't require a massive food court, so space food and drinks in a way that allows guests in every corner of the park to satisfy their needs when necessary. Your greatest income will come from non-consumable goods, especially park maps, umbrellas, souvenirs, and especially balloons, which guests will let go of and purchase again - these can be an endless source of income!
Once this is done, you will be able to concentrate on your objective, which is no easy feat. You'll needed to have amassed 3500 guests in your park by the 31st of October, year 4! This renders it one of the hardest objectives to meet, more than Amity Airfield in the same time span, and harder than the American Six Flags scenarios on which you're given unlimited time for the same goal.
The first thing you might notice about this park's layout is bad usage of available space. There are many large open areas just waiting for a few thrill rides or a new coaster to be dropped onto them. Though you won't make any money directly from these rides, the new guests that they'll bring in to the park are more than worth the expenses of construction. The more guests you attract to your park that stay there, the more you can make money off of shops and stalls!
If you're struggling to attract guests, remember that deleting a ride and replacing it will cause the guests to see it as a brand new ride! New rides, especially coasters, can bring in hundreds of new guests, so consider this if your options seem to be wearing thin as the end of year 4 approaches.
After that, just keep on advertising to make sure you have at least 3000 guests in by the end of year 3. If you're not meeting this criteria, cancel all of your big building plans for the next year and spend every dime you get on advertising. Once the objective is met, feel free to build new rides, improve the aesthetics of your park, or repay your loan.