Finding a model to use—whether it's in a published formbook or a provision that has been used in practice—is only part of the work of drafting. You also need to make sure that the terms you are drafting fit with the law. Is there a consumer protection law that affects the contract? Does an anti-usury law limit the interest that can be charged? Have similar contract terms been litigated?
Treatises—in print or online—summarize the law, backed up with copious case citations in footnotes. They exist in all major areas of law, including banking, contracts, corporations, and employment law. Other practitioner materials (continuing legal education materials, manuals, deskbooks, etc.) are also useful.
Note that treatise publishers generally only license them to one online service, so you won't find the same treatise on, say, Lexis and Westlaw. Westlaw (owned by Thomson Reuters) has treatises published by Thomson Reuters; Lexis has treatises published by Lexis Publishing; Bloomberg Law has treatises published by the ABA, BNA Bloomberg, and Practising Law Institute. Because of this lack of overlap, it is often worthwhile to search in more than one service (as long as your are a student and the library provides you with unlimited access to all three).
ALR annotations provide very brief summaries of cases, from around the country, on focused topics. ALR is available on both Westlaw and Lexis.
Legal encyclopedias summarize black-letter law, with footnotes citing zillions of cases. Am.Jur.2d is on both Westlaw and Lexis, but it is updated more frequently on Westlaw (quarterly versus annually) (because it's published by Thomson Reuters). C.J.S. is available only on Westlaw.
It's generally most efficient to start your search for cases by using secondary sources, because they will give you an overview and organize the mass of cases for you. But of course you can also search cases directly, in Westlaw, Lexis, or Bloomberg Law.