Hes including the keyboard, mouse, and monitor for 250.00
And by what you saying 150 for a newer motherboard and a DDR4 for another 100 is not that bad of a gap, i wanted to initially invest 1000 into a PC
This is honestly a good base price considering whats included
Be careful and research that upgrade before buying because typically you're not going to find a new motherboard that supports an 8 year old CPU AND the newest RAM specification. And even if it you can you immediately make your CPU your bottleneck leading to........ a cpu upgrade, which is what you could do in the first place by buying a new machine.
The problem with trying to upgrade much older hardware is that you wind up paying the same or even more than current gen prices for older/worse hardware. Once the generation changes and the hardware becomes outdated, you can wind up paying a premium to get it. It's not bad if you're a generation behind and just need to update a stick of RAM or cop a better processor that you just pop in, but once you swap that motherboard, you have to definitely consider the cost of upgrade.
$250 for the computer + $250 for upgrades isn't going to get you a better machine than building a machine brand new (or doing like I do and buying used parts individually). The only consideration would be if you don't have a monitor and keyboard and when then you could do a dual monitor setup for less than your $1000 budget.
Most barebones kits you can find on Newegg or TigerDirect can get you current hardware for not too much more than you'd pay for that old computer.
I went thru the same thing years ago with my LGA 775 mobo and threw it to the bushes after comparing the cost to upgrade the ram (which would eventually lead to a new Mobo and processor) to just buying a more current generation of hardware.