I'm using my VA loan so I don't have to put any money down & can keep money in my account to fund rehab deals. 

Quote from @Guadalupe Batana: Learning about different types of loans is always a smart move, especially as an agent.

It recently dawned on me the idea of a non military affiliated individual assuming a VA loan, would this individual be able to then also gain the benefit of using an IRRRL since they have now acquired a VA loan through assumption?

Review Anchor Loans, they have closed many investors I've worked with.

I know that interest on the acquisition loan can be included in the cost basis since it’s inventory.

Start by getting pre-approved for a loan, ensuring your credit score, debt-to-income ratio, and finances meet lender requirements.

Here are some thoughts on your choices:401k Loan: This can be a good option since you're borrowing from yourself, but it comes with repayment risk, especially if you leave your job.

It may or may not show on a credit report, depends on the servicing and you should have the loan serviced.Failure to include the debt on a future loan application is mortgage fraud, wanna go to jail?

The typical term of this loan is 12 months and rates range from 10%-12%.

Are there specific lenders or servicers that are more likely to call these loans?