Not to mention the increasingly large families over the years.

I want to have a few multifamily properties to increase my income per door so I can hopefully retire much sooner than later.  

I do all of this for the long term gain (increasing rents and thus cashflow, along with appreciation).

Could probably increase the rent by $100 after the current leases are up.

Since then, I have fixed it up a bit (put in about 35K to increase rents).

You seem to be confident this is the right market for you and you believe your mentor is steering you in the right direction.

There are credit forums with all of the tips needed to increase your score (keeping accounts open, increasing credit limits to decrease debt ratios, disputes, etc).

Not sure how much of an issue that would be for you (it would deter me) Another strategy would be to find a multifamily that would pass VA inspection, that needs work and you can put some money into to increase its value.

If you believe that things are as they always will be, (first you should look at the past and see if that is a reasonable assessment of what the future brings) then taking into account: limitations on what you can invest in, your Solo 401(k) "projected" growth, fees & hidden fees, you can't co-mingle funds, you have to carefully manage the process, future tax increases, tax law changes, a national debt that is north of $22 Trillion dollars, unfunded liabilities and and of course inflation, along with possible "bail ins" then you are well equipped to decide if that is a good choice for your style of investing.However, If you are an "opportunistic investor" . . . . you jump at the opportunity when it arises, then you run into some conflicts.

We can increase rent to match the area, but it is already cash flowing.