A mechanics lien doesn't involve the transfer of any money.

The transfer in and out of your llc can be considered a change in title and can make it more difficult to refinance too.  

My long-term goal is to build an investment portfolio of 25+units Sfr, purchase a 50+ unit apartment complex and enter franchise & international investing, creating complete passive income streams for myself, allowing me to travel, volunteer and educate.

To me that just isn't worth it financially, I think there are many other jobs you can do to get a decent salary and simultaneously invest in RE or other businesses, which will put you miles ahead of most doctors.It really comes down to where your interests/strengths are, what you prioritize, and your true internal motivation. 

If this opportunity were to come to you, what method(s) would you use to structure the financing of this "international" purchase?

Review as many internal docs as they'll allow.

His company is Prime Transfer.  

I have focused my research on buy-and-hold SFRs in what I would consider B neighborhoods (UPS, Proctor) and B-/C+ (neighborhoods surrounding the International district) neighborhoods.  

I have focused my research on buy-and-hold SFRs in what I would consider B neighborhoods (UPS, Proctor) and B-/C+ (neighborhoods surrounding the International district) neighborhoods.

All those things you replaced in 2013/14/16 will eventually need to be replaced again, so add that to your numbers.If you sell it now, could you generate more cash flow transferring the equity into another property?