I’m running the numbers and thinking the whole traditional method of buying a rental asset and it requiring very little active work, generating significant sustainable free cash flow over a long period of time, does not exist.

If you purchase a property with a VA loan, but it doesn't cost as much as the maximum eligibility price in that area, than you can borrow again at a later time on another property up to that maximum.......another, If you move after the one year and want to apply for a new VA loan, you can refinance to a traditional loan on your first property and you free up the entire VA loan eligibility. 

I would think this would be less risk than traditional office space.

Roth IRAs cannot be transferred to Solo 401k plans.A few other Solo 401k benefits: Compared to an IRA, Solo 401k contributions limits are roughly ten times higher.There is no custodial requirement for the 401k.You don't need the additional expense and administration of an LLC to have checkbook control.There is a built in-Roth component whereas IRAs are either traditional or Roth, not both.A spouse can also participate in the same Solo 401k plan.The Solo 401k has additional tax benefits over an IRA when investing into real estate using leverage.

As traditional small B&B's are, my house is an owner occupied income producing property, but it doesn't fit into "residential" loan requirements.

If you're self-employed, the Solo 401k will provide many benefits over a self-directed IRA: Compared to an IRA, Solo 401k contributions limits are roughly ten times higher.There is no custodial requirement for the 401k.You don't need the additional expense and administration of an LLC to have checkbook control.There is a built in-Roth component whereas IRAs are either traditional or Roth, not both.A spouse can also participate in the same Solo 401k plan.The Solo 401k has additional tax benefits over an IRA when investing into real estate using leverage.The penalties for prohibited transactions are less severe, though it's best not to utilize this benefit :)

Or do they use traditional methods like going on LoopNet?

Before exploring it, it's important to note ARV is a construct used more with asset-based lenders than with more traditional, credit-based lenders, where LTV or loan-to-value is one that is more prevalent. 

The Pros of a traditional buyer is that they may offer a higher price than expected especially in this market the con is you may need to make some repairs, but, they may be a few quick fixes  the whole process could be easier than you anticipated.

You can prove your income using bank statements versus the traditional tax returns (personal & business) , W2's and 1099's.