There are usually multiple strategies to successfully completing a scenario; these can be discussed on the scenario's discussion page or written down in an existing or additional section of this article.
First off, open all of the rides and hire a few mechanics to keep them operational. If you need to delete any of the pre-built rides, demolish the Mine Shaft Screamer. Keep Mining Mission, as it satisfies all the coaster requirements up through Tycoon level. Also keep Dynamite Danger, as it is popular and helps your ride income. For the first roller coaster you need to build, build it in the large space to the right of the entrance. Then, build another one at the top of the hill at the back, and use its height to send it anywhere you like inside the park. Lastly, increase the prices on all the rides, build a few non-tracked rides if necessary, and then pay off your loan. With luck, you should beat the Entrepreneur and Tycoon levels at the same time.
An easy way to get a steady income is to build four or five thrill/gentle/kiddie rides right near the entrance in a compact area, equipped with its own fully trained janitor (set the path) and mechanic (set his path) and food/drink/bathroom stalls. Don't forget to adjust your research to fit the objectives. In this case, you can pretty much just eliminate all other categories and only have your blue bar for roller coaster research. The four or five rides technique can be done in every level with positive results. It is self-sustaining and a very easy way to raise ride income. With that ride income, you can build the required coasters (you can use pre-built ones easy enough).