How to get to "the next level"?

[Jason J Zabka]

2 years into this venture and we have 2 properties.  A single family and a duplex...cash flow around $1k/mo.  not counting repairs and unexpected expenses. Also purchased our residence last August.   Have already refinanced 1 rental and not enough equity buildup yet to repeat.  Have $15k in business cash reserves and around $25k personal. Also around $80k in retirement funds.  Wondering how to attain more properties besides just saving and waiting to have enough cash.  If we use our reserves to make a down payment on another rental, it will wipe us out and we'd have nothing for repairs/unexpecteds.  Considering borrowing from 401k.  I'm just wondering if there's a "next move" I may not be considering.  Not sure if I want to take on the risk of a flip, although we are considering it.  Any replies or referrals to existing BP threads would be HUGELY appreciated.  Thanks in advance!