how can i buy and sell a condo, townhouse or a house with zero money investment? I know that’s possible but i want to know how? Thank you!

I want to know the details about what the property characteristic which can considered as an investment.

I want to invest in real estate but want to protect my personal assets.

I am just starting out in real estate investments, and do plan to get a real estate sales license. I was wondering what would be the best route for the beginner.