Joe
If you are building hours towards a particular threshold but then looking to progress into a different avenue of aviation (eg hours building to CPL etc) remember that aeroplanes are not easily tradeable commodities. Selling takes time, maybe more time than you have. There is not exactly a huge number of people who can afford to purchase aeroplanes.
As has been mentioned earlier in this thread, buying into a Group is like a marriage - but it is also business. Treat it as an investment to the same extent as you would closely scrutinise any private investment. If the rules of the Group seem unclear or informal, be aware that if you have a dispute, you may be up for a lengthy battle with your co-owners - with your hard-earned money sunk into a share of an aeroplane - resolution of which requires expensive legal help. If you treat your co-owners as business partners first, friends second, you may avoid falling into situations that can result in heartache.
All that said, there are many very professionally run Groups the rules of which are crystal clear - if everyone knows the score, there is less scope for confusion or disagreement.
By the way, don't be put off by the stalling characteristics of a PA38 - it makes it a much more interesting aeroplane to fly than a 152 and sharpens your reaction-times. It has much better visibility too!