I know there are a lot of benefits to opening a business, and that I have a 2-year window before making any actual earnings that I can still get the benefits of write-offs (vehicle, office, repairs, etc.).

He knows that this property isn’t a good deal in today’s market for investors and that selling to the current tenants is his best option, but because the tenants he is hoping will buy it (bc they expressed a desire to do so) are having a hard time qualifying, Im just trying to help him determine the next best move if that doesn’t work out - the one that will benefit us the most now that we are real estate investors.  

The loans I get are all commercial, with a personal guarantee.One benefit here is a single credit pull / application.

It is an invaluable skill that will benefit you tremendously. 

I've been searching and trying to learn more about the refinance benefits and how to tackle lenders.

Is there any benefit to purchasing this all cash as opposed to doing a 3.5% plan? 

If they have a lease, they get the benefit of the duration of the lease (Assuming its a legitimate lease).

For our primary mortgage, we are 2 years into a $600K 30 year 3.75% fixed conventional loan.Here are some pros and cons I can think of for each option:Invest as CashPros:Very liquidLess riskyNo interest on cash amount for next investmentKeep higher primary home interest expenses for tax write offCons:Sits in savings account earning 1% until reinvestedPay Down Primary Mortgage and Take Out HELOCPros:Saves $275,000 interest and reduces payoff during to 15 year on primary mortgageCons:Puts primary home at risk if future rental property investment goes badHigher and variable interest rate on HELOCBanks could close HELOC at any time removing my access to the funds for investmentMiss out on tax benefits of higher primary home interestUltimately, our goal is to have no personal debt including primary mortgage, while building a steady stream of cash flow through rental properties over time. 

If you're self-employed, the Solo 401k plan will likely work better for you.A few Solo 401k benefits: Compared to an IRA, Solo 401k contributions limits are roughly ten times higher.There is no custodial requirement for the 401k.The Solo 401k can allow you to borrow funds from the plan, unlike with IRAsYou 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.

Is there a lot of benefits in integrating a construction company into a real estate company?