Just done a Bit of Research for parts Based on what's listed in the ad for what it would need (Assuming there's nothing Hidden/Extra, it would need Tires, Front & Rear Brake Pads, Front & Rear Sprockets & Chain, Battery & Exhaust Headers), Looking on fortnine.ca for the Cheapest Brake Pads, Battery (Without Acid), Sprockets & Chain it would cost a grand total of $243.37 (After Tax & Free Shipping), Tires are Variable based on Size & Bike Style but the Cheapest Front Tire in stock Size (110/80/17) would cost $77.99+Tax & would be for a Cruiser, the Cheapest Rear Cruiser/Touring Tire in Stock Size (140/80/17) would cost $238.99+Tax, With those Tires the new Grand total would be $590.26 however choosing the Cheapest Rear Tire regardless of Bike type in the Stock Size would be $103.99+Tax for a Dual Sport, with that tire instead of the More Expensive Cruiser/Touring Tire the Grand Total would drop to $437.71 for everything except for the Exhaust Headers (Couldn't Find Any New, only Used with the Cheapest I could Find on Ebay being for the 1998-2006 Model while it would need 1988-1997).
TL;DR it would likely cost roughly $450-600 for Everything Except Exhaust, if the Bike can be had for free than that would leave roughly $550-400 to get the Exhaust, Install all the Parts yourself & Overall Spend Roughly the $1000 it would be worth (However depending on where/how & New/Used it's possible to spend less than that)