Yes, if commuting into Manchester, there is no train from Lymm. Yes you could drive to Sale (or Altrincham or anywhere else on the tram line) but its not cheap to park (for instance, parking in Altrincham has gone up to £7 a day and the tram is £6.50 a day). Of course you can try to find a residential street where you can park but it means getting up early to get a spot, or parking a bit further away and walking to the tram.
You definitely get more for your money in Lymm than you do in Altrincham / Hale, £550k for a 4 bed isn't a bad price. Lymm is lovely, the village centre is very quaint and Lymm Dam is lovely. As others have said, there isn't as much going on as Altrincham or Hale (really buzzing at the moment with Altrincham Market etc etc) but Lymm has more countryside and is more picturesque.