What is the least amount of money that you could get away with? Do you even need a lawyer for a seed round if you're not doing anything fancy?
Even if raising money with a convertible note, and using the community documents, you'll still need someone to file your Form D, prepare your board consent, and ensure all i's are dotted and t's crossed. You don't want to run afoul of the SEC.
Is your corporation established? Are you authorized to sell shares?
If you bring your own paperwork, you should be able to get away with <= $5k via a negotiated fixed price or cap on the legal work.
Some firms are also willing to defer payment up to a certain amount and/or until you raise additional funds down the line.
Check with your school. Perhaps they have an entrepreneurship program that can help?
I recommend using something like clerky.com for incorporation and post-incorporation setup. They might also be able to help you with the later parts of the process.
As far as the cost goes...you gotta spend money to make money. Don't do any of this until you're absolutely sure that you have committed investors, and you'll minimize your risk.
The "people I trust" part is important, as is the "that I know and understand" part. Common sense dictates that you probably don't want to take investment on terms given to you by a total stranger that you don't fully understand.
If you've never done this before and/or you don't understand the docs you're using, you should probably consult someone who does.