You can always rollover Traditional IRA and old 401k into Solo 401k, if you qualify to set one up, you can learn more about qualifications in this blog post:https://www.biggerpockets.com/blogs/2810/45144-the...

It does not have to be an ongoing qualification.

If you contact a hard money lender, they can typically provide you a qualification letter for your offer to help you submit a stronger offer.  

If you are going to occupy, then you are correct, timing is everything (especially if you are currently renting and have a lease).The current owner would handle a vacancy contingency by offering cash for keys to vacate prior to closing, or they may be month-to-month tenants.Some lenders will allow a renter credit toward qualification for owner occupied properties.

People can click on your webpage and see the following:Where the property is locatedHow much it rents forIf it has good curb appealWhat the neighborhood looks likeWhat is close to the home as far as stores etc.When you will be doing an open houseWhat the qualifications are for the homeWhat time you may be showing itHow much it is renting forEveryone wants to be a landlord these days. 

They must go through the qualification criteria just like anyone else.  

@Shawn Root there are two qualification criterias for the Solo 401k:1.

I have recently been pre-qualified for a loan of $125,000 to buy investment property. I'm planning on selling my principle residence, move and buy a new principle residence in my new location. If I buy an investment p...

The reason for this is because in the past the minorities were always found not to be the "best" applicant.Every application we give out has our qualifications attached to it and the prospective tenant should know if they qualify or not.

I emailed them my list of questions (seller qualification form) and come to find out that this agent only "listed" the property for a flat fee, and offered to represent me and get me the info that I need, CMA, etc.I told them that I would sign a non exclusive agreement for the two properties in question.