well, i did 3 houses that stretched the budget & needed doing up. in the midst of it, there really is a black pit of despair - specially if the bathroom of kitchen are being done. but once it's done, then it's so lovely you fall in love with the house all over again.
sadly, i've only reached this stage just as we move out (in fact, dh had already moved out of one house, on to the next job, while i finished the house & saw out my job contract)
i have, quite literally, sold a house whilst the paint is still wet.
if you are 99% certain that you're staying in one place for a while, i'd buy the bigger home. moving house costs a LOT - you need to budget at least 15k for it, and that would go a long way towards repairs. so long as there is nothing structural that needs doing, you just have to live with how it is - or just v quickly paint everything white to cover it up.
you need to live in a place for a while before you really know what needs doing - e.g. you'll notice if any cracks are getting bigger or not, or realise that a certain room/door gets more use than you expected, so what if you move that wall to ...
you can move into the bigger house, and just save every penny towards getting the work done, and don't start a job til you know you can afford it.
if you've done this before, you'll know what you're letting yourself in for. if you haven't, don't underestimate the hard work - it looks so easy on tv, but it's exhausting & demoralising & expensive. you will have less time to spend with the kids, less time to see friends etc. that said, if it gets you into a long-term family home with one move, it IS worth it both financially & emotionally
if you are doing this for your family home, Don't try looking at possible market gain - it's irrelevant. you can't predict if it will rise & fall in value, just focus on what you want to be doing with your lives for the next 5-10 years.