Beginner business setup question

[Brian Falcon]

I've been listening to a lot of BP Rookie podcasts and many folks on the interviews say they buy all their properties in their personal names (single- 4 plex types).  Then some also say "I reinvest all my money back in the business".  These seem contradictory to me - how would a business be formed around owning properties in your personal name?  Is that legal, or wouldn't you need those assets owned by the business?  How would such a business be structured and how would the accounting work, if funds are coming from personal accounts? I have my old home as a rental and am trying to figure out how to set up all the processes and systems in the most efficient  mannner before I scale.  Any advice would be greatly appreciated!