How many single family homes should i put under a LLC before i need to start a new LLC?

Depends on equity. If there is no equity then there is little risk. If you put 10 homes under one LLC then they can be all exposed in the event of a lawsuit to one of them. Split them into series LLC if allowed by your state or individual LLC.

Look into a Series LLC. In many states you can now give each a separate llc without a lot of extra expense.

@Thomas Hage Typically my clients will choose to place one property in its own child series within a Series LLC. This provides optimal protection as you achieve separation of assets. You can check out Podcast #109 or review this article to learn a bit more:
https://www.biggerpockets.com/blog/the-traditional-llc-vs-the-series-llc-which-is-better-for-real-estate-investors/

Also feel free to leave a reply or send a DM.  Happy to help with any questions you may have.