Welcome to the forum. Honestly, we cannot give many of the things you ask for. Whether or not we think it would be a good investment, and how much you should put into it, we can't really determine. If you want to find out the best options for this house, look around the area where it is. See what houses have SOLD for (not are selling for, sold for, your realtor should be able to help you with this). If the house prices support the 250k purchase price plus a 250k renovation, then you are good on that point.
However, its impossible for us to estimate the cost of just simple repairs to this house much less a complete remodel. Prices of labor and materials vary a lot from one place to another. Plus we cannot see the house ourselves, videos dont have the best lighting, we cant see the ceilings or up close to walls/roof/floors. Based on some of the things they are showing, the house has water damage, which could mean replacing a roof, replacing floors, walls, electrical etc. Your best option to get a good estimate is to bid on the house and see what you can manage to get it at. Make sure your contract allows for inspections and your right to refuse should the inspection come out awful.
After the inspection is completed, you can also call out contractors to get estimates on the repairs. Make sure you have lots of time in the contract for you to inspect and get contractors out (1-2 weeks). Get as many estimates as possible, then add them upp and add on another 30% and thats probably going to be close to what your final cost of all the repairs are.
A few other things I would like to point out, if you dont already know them. In the condition this house is in, and how the market is today, a bank will likely not finance the purchase. Meaning you would probably have to purchase as a cash only deal, you may be able to talk them down A LOT by doing cash only, but its going to have to be cash. Or its going to have to be a difficult to get loan. Fannie Mae offers repair loans, there are also 203k loans. The fannie Mae is better, but it must be your primary residence and you have to have at least 3 credit cards with 2 years of good history on them. The 203k is less strict from a credit history perspective, but you would have to have a house estimate done and whatever repairs they note need to be completed, you would have to complete within 10 days of closing.
I noticed you also said the house has been on the market over a year, be very wary, odds are there is a lot more wrong with the place than you think there is.
From the video, some of the repairs I can see coming your way, replacing all the flooring in every room, this could be as cheap as 99c a square foot with cheap flooring you install, to $5 a square foot for medium level flooring installed by someone else, to something much, much higher. The windows are probably going to need replacing, for an insulation perspective and it looks like some of them have holes. I thought I saw some bulging in the walls (Cant be sure, bad lighting). Which could be something as simple as water damage (most likely since there is water damage elsewhere) to a bad structure that is sagging (Just walk away unless you want to level the place). You will probably need some drywall work. The kitchen didnt look too bad (it looked newer but the lighting was dark I couldnt tell if they were old cabinets or not).
From the video I couldnt get a good idea of a layout, if the layout is awkard you may have to rearrange rooms some or move walls. If its really badly set up (as in you have to go through rooms just to get to other main rooms) then you might just want to consider letting it go. Many people will expand houses by adding on rooms into awkward places, it adds square footage but once a buyer sees it, they figure out why the big house is so cheap.
I think its got some nice features, I like the spiral staircase, I would rip off the carpet and see whats underneath. I also like the cove in the blue room, and the nice brick exterior (though I see some eflo on it). It could be a good investment, it could be a horrible one, your first step is to figure out what it would be worth in good condition, then figure out if its possible for you to get it there without losing money