Old 401k to Solo 401k or Old 401k to New 401k transfer?

[Anna L.]

Hi, I am newbie (just had my first successful flip). My plan is to start using 401k $ to fund next flips or buy and hold deals. 

Here are the two options I am thinking about: 

1. X-fer from old 401k to Solo and start investing

2. X-fer from old 401k to new 401k and borrow for future project

Here is my dilemma: it would take me few months to understand all the details about investing using Solo 401k. So, I don't feel comfortable to x-fer $ from my old 401k to Solo 401k yet. But, I know that I can only use prior employer 401k funds to do so. Now, I can x-fer $ from my old 401k to my new 401k to maximize the amount I can borrow. But I am afraid that I will no longer have an ability to x-fer to Solo 401k in the future, because all the funds would be with my current employer. 

Which option would you go with?

Thanks!