I need a reliable Motherboard that has SLI support and is under $100 if possible.
You can screen SLI capable mobos on PCPP by SLIing cards in your parts list, and then filtering for lowest price first.
Buying old motherboard will not benefit you.
Buy one of these cheapest and reliable boards....costing 134.99$
Intel z97 chipset
There aren't really any. Gigabyte has the GA-Z97X-SLI for pretty cheap, and the ASRock Z97 Extreme3 occasionally dips to ~$105.