There is no legal limit, but there is almost always a practical limit because a sponsor can only deploy so much money before they have to lower their underwriting standards etc.

Hello! I am a real estate agent new to real estate investing and need some advice -  
1. Which NAICS code should I use for my activities?
- Residential purchases, remodel/repairs, and re-sale (flips). I'll typically...

Quote from @Kevin Reinhardt: Best practice: screen and approve every adult, whether they work or not, and have them all sign the lease.I highly recommend you purchase "Every Landlord's Legal Guide" by NOLO or "Managing Rental Properties" by Brandon Turner.

And without knowing your full financial situation, it's hard to give you really practical advice.

I've only ever done rehabs (with some so extreme that they were practically new construction!)

Whether that be through marketing, consulting, or other practices, I would just like to learn as much as I can about the industry.

I don't think private lenders would have this requirement, unless title companies encourage wet sign as standard practice.

I've narrowed it down to the Birmingham, AL and Cleveland, OH markets and have been looking at properties in these areas and "running the numbers" for practice.

Promising to make cosmetic upgrades that one should only make between tenants and reducing your already below-market rent down another $3600 are not good business practices.

Clearly practice makes perfect, but if I can learn from your experiences, it could save me some grief!