However, I'm not opposed to looking at BRRRRing SFHs because I have a few friends that had success doing that as well (obviously there's less cash flow/leverage when it's not MFH). 

If you're not opposed to living the apartment lifestyle since you're still young enough to tolerate it :), you might look at a 203k loan to rehab a tired 4 plex wherever you decide to live.

If you are asking if one strategy is riskier than the other then  the answer is mine is but thats only because of diversification alone.I think what you are asking is  what is the  riskier strategy. the only time my strategy would benefit me and hurt him is if the banks start having problems. for example if the bank calls the loan due for some strange reason he would be in trouble as opposed to me where I dont have a lender. 

., but to specifically answer your question it is less expensive but riskier to go to 15 year mortgages as opposed to snow balling.

I am nervous and unsure as to how to approach it being that not only is this my first deal venture, but I also am not 100% sure how the seller finance process works legally and through documentation as opposed to a traditional home loan.

I'm definitely planning to buy based on the numbers as opposed to appreciation.

Likely 1 primary residence then 9 rental properties.After that i'd suggest using additional capital leftover to purchase commercial properties as opposed to paying off those residential mortgages early.

The 10 loan limit is related to the secondary market, so if you have more than ten personal loans, you at that point may want the LLC to get business / commercial terms as opposed to personal / residential terms. 

She has found me the best deals out there (I have yet to buy one) as opposed to the other agents.

You only need to put 3.5% down, so cashwise it won't get in the way of other real estate goals you may have.My first deal was a 4-unit up I bought withFHA3.5% in Santa Clarita.I lived for free (as opposed to paying rent) + enjoyed cash flow + built equity.