Do I have to pay tax?

I do not practice law in your state but your question seems to be more of an accounting question than a legal one. Also, where is the money being transferred from? This may make a difference as it relates to your tax liability. Please seek the advice of a tax attorney in your area and an accountant. I wish you the best.

When you receive money it has to be characterized as something. It may be a gift, in which case the transferor - your partner - should file a Federal Gift Tax return (IRS Form 709). However, you do not have taxable income. It may be the payment of compensation, in which case your partner may have a deduction an may need to issue a 1099 to you; and you, of course, have taxable income. It may be the repayment of a debt (does your partner owe you money)? It may be that your partner is just having you hold the money for a joint investment, e.g., your partner is investing $60,000 and your are also investing $60,000, so it is a 50-50 investment.

The point is that a transfer of funds can result in more than one tax treatment. So you should discuss this with your CPA. If you don't have a CPA, then discuss this with the person who prepares your income tax return. If you prepare your own income tax return, then you should get a recommendation from a friend, relative or business colleague. This is not the type of advice to get over the internet.

If you are buying a house in both your names, the transfer is not a gift to you, but rather he is paying part of the down payment on the house. You should definitely have an agreement whereby you agree as to what that money is--either his part of the equity, or a gift to you, or a loan to you. That way, when you sell the house, it will be clear where the proceeds should go.