You can borrow as much as you want without any tax implications for you. Money that you borrow is not income, and you do not report it on your tax return.
There might be tax implications for your friend if you pay back the loan over time. Part of the payments that you make would be considered interest, which is taxable income to your friend. Even if you and your friend agree that you will not pay any interest, the IRS considers part of your payments to be "imputed interest."
Imputed Interest: What it is, How to Calculate, FAQs
The following TurboTax article is written from the point of view of the lender, not the borrower.
IRS Tax Rules for Imputed Interest
