Whereas in LLC, each partner can withdraw what they want and only his/her basis would be impacted.3)In S-corp, you act as both employee and investor.

Which path is "best" will be specific to many details of your situation and goals.401(k) funds could go do a tax-deferred self-directed IRAIf you are self-employed and have no full time employees, a self-directed Solo 401(k) may provide additional benefits beyond just more control and flexibility of investment choices.In either an IRA or 401(k) format, you could also consider doing a Roth conversion.  

Has anyone had any success finding financing options while self-employeed?

@William Collins here in this example:https://www.biggerpockets.com/forums/223/topics/445367-full-time-employee-multiple-brrrr-side-hustle-2875-to-goal...shows how he used $150,000 down payment to acquire 9 houses in 2.5 years.

@William Collins was just discussing his first 9 successful purchases/refinances here:https://www.biggerpockets.com/forums/223/topics/445367-full-time-employee-multiple-brrrr-side-hustle-2875-to-goal

I told them I would find another tenant other than their employee, and tell the employee why.

Tenants like an employee.

The following link to the IRS website should be helpful: https://www.irs.gov/retirement-plans/plan-participant-employee/retirement-topics-prohibited-transactionsHaving the multiple lenders that are disqualified persons to each other (but not to you) should be all right.

And when I compare the expenses generally people are paying higher expenses for the larger properties per unit because they have levels of employees. 

As a W-2 employee with a strong base salary and credit, would I be able to buy the property from my own LLC and get a mortgage in lieu of a Refi if numbers get tight?