1984 honda magna v30 500?

Here's the what the add says:
"1984 honda magna v30 500 - $800
I'm selling my 1984 honda magna that currently has no gas tank. It runs fine, but I don't have the time or need for it anymore. Little over 15,000 miles, good tread, brand new forks seals and battery (last fall) , seat is in perfect condition, the tank rusted out on me end of last year and haven't been out on it since. Great little bike for around town and beginners. You can get tanks on eBay for around 175 (fits the 1985 magna v30 tanks too) and they are easy to install. Listing if for $800 obo, or if you want I would be happy to buy and install the tank for $1050."
What are some things to keep an eye out for when looking at the bike (Things that could need replacing or make this a terrible buy in terms of repair)?
Thank you

You should pass on it. Never buy a bike that isn't running unless you're a good mechanic. Also keep in mind bikes that old ARE going to need work. Parts can usually be found, but they can be very expensive. If you can't do the repairs yourself the bills could easily end up costing you as much as a newer bike.

Could tell seller you'll buy it after tank replaced and can see it run, test ride it for $1000.00. Check out 'as is' and see if engine turns over, bring a experienced rider with you and a peanut tank to strap on for running engine test, might be worth $300.00 to $500.00 then. Last year at end of season a Suzi 550 with good rubber was started and ridden to auction wagon, driven around lot and sold for $325 or $350.00 at auction. 1949 and other later date Dualglide frame, upgrade engine 1970s dated parts Harley went for $3200.00 and a second late 1970s Harley went for $3750.00- all driven off. Parts bikes are $50.00/$150.00 or so- what a salvage yard will pay for good front ends, frame for the mid season frontend damaged crash repair parts needed.