Solo 401k, IRA, or other to start using for rentals?

[Jeremy Karja]

I currently have an IRA I converted from a 401k I would like to use for investing. My plan is to use it for the BRRRR strategy with the money and start rolling into other properties after I refinance the first one or two I buy with my qualified money. The question is should I use a loan from a 401k or should I use my IRA for the down payment and all other costs?