Which is the best scenario??

[Account Closed]

Hello, I am looking for some help to be able to figure out which approach is the most tax efficient approach.

Here is the scenario...

I have 300,000 dollars which I am going to spend on a Duplex. I am planning on renting the duplex for 2800(which includes both units). I am planning to buy this unit with cash. I plan on holding this unit for 7 years at which time I want to sell it.

Assumption:  I can use PreTax money or I can use PostTax money.

Question: What would be the most tax efficient strategy for me to use?

1. Use a SD IRA to buy the property?

2. Use a Solo 401K to buy the property?

3. Use after tax money to buy the property?