What documents do they require, what credit scores do they allow, how do they verify previous rental history, etc.?

The reason people do sub2 is to get around this requirement and not notify the lender they are transferring the asset.

An LLC requires time and money to create and maintain, every year. 

I’m open to any advice, personal experiences, or recommendations for someone at the beginning of their real estate journey!

I recommend that you engage with a real estate accountant to ensure you set everything up properly. 

I also recommend The David Greene Podcast on YouTube because he is the most genuine, honest educator out there right now.4.

Today, that building generates enough passive income to cover his annual retirement contributions.You mentioned taking the 10% penalty, which I’d only recommend as a last resort.

Some carriers require limited water damage coverage depending on the age of the property and age of utilities.I would recommend at least 25% (ideally more) when possible and if you're limited to 10% you should make sure you cannot purchase another policy for a similar price.

I just had a bank tell me that per new Fannie guidelines, the minimum down payment on a 3-4 unit is 20-25%, even if it is bought as a primary residence. Personally, I think they are wrong. I think they are just an ext...

@Mike Terry recommend before buying - find a reputable PMC!