Also keep in mind that in many cases the home is not in good enough shape to pass an appraisal, therefore you would need to purchase all cash in order to buy it. 

I am "worried" that I won't be able to find deals that are good enough to meet my strict criteria frequently enough to stay on pace for my 5 year plan.  

Many investors are willing to do this if the deal is good enough. - Lastly, just take action.

Hard money is generally less expensive than the 25-30% tax bracket most folks with a good enough job to have a 401k are in, and that 25-30% is what that loan is really costing you.A solo 401k is a fantastic program if you are self employed, as it provides a great opportunity to build your retirement on either the tax-deferred or Roth side, and the ability to invest as you see fit rather than being limited to what the guys on Wall St are selling.You are correct that there are some restrictions when you choose to invest your IRA or 401k into real estate.  

Then you need to know if the properties are in good enough condition to get market rents or if they need rehabbing.

I'm open to investing pretty much anywhere if the deal is good enough.  

Ease of exit, possibility of appreciation, generally longer tenancies and superior tenants, etc.Really, you should evaluate every prospective deal on its own merits, and not worry about whether it is "good enough" relative to other hypothetical deals that are not in front of you.  

If none of them are good enough or not to your liking pm me.

It's not that expensive, and it looks good enough.

If you can get a good enough deal on it, and convince someone with money that you have enough experience to manage a property like that, then it’s that easy.