I stayed in a hotel which was 5 minutes walk from the border - I can't remember what it was called but it may have been the Ohtels Campo de Gibraltar based on a Google search
The Ohtels was originally an 'Iberostar', then it became an 'Asur', now it is Ohtels. (It may even have had a 4th brand in there, but I don't think so.)
That hotel is perfectly walkable, but I'd suggest the OP sees if they can get a deal at The Rock, The Eliot, or the Sunborn - this far out.
However there is not denying prices are lower in Spain, as there is simply more land available, also wages are a little lower, but it is more land prices.