@Taylor Colligan Yes it can be on an investment property. And yes it has to be your primary residence.
So how do people use 2 VA loans? They move, they satisfy the requirement the lender requires them to live in the residence for. Not all VA loans are alike. People think they are regardless of which lending institution offers it but each lender will have their own stipulations.
Example from my life: my lender said I could buy it and live in it for 3 months then move. Moving is a part of life and that's what makes the VA loan great for veterans, we move. So I buy property with VA, move in, live in for specified time, move, (most likely to a new city, not close my understanding, you can't just move within the city) then use the remainder of the VA loan for the 2nd property.
So real world, we're buying a property here, then moving across the country in aprox 1 year, we'll use the VA loan again to buy another home. If you're staying in the city and want to use the VA loan again you need to refi the VA loan or sell the property. You can refi to another loan if you put sweat equity into it. Example, I buy a perfectly live-able home at a discount because you walk in and holy crap it's the 80's! I renovate using my cash on the home and a year later, its worth more due to the upgrades and me bringing it to market value, now I refi into another loan product.
Hope that helped, but VA loans go from one point to the next easily. and they can be confusing. Talk to a lender in your area to see what they can do