Another thing you might want to consider is this; by doing a type rating you are effectively putting all your eggs in one basket. If you decide that the 737 is the type that will make you most marketable, then you are closing all other types from consideration.
It is unlikely that turboprop operators will be interested in taking on someone who will, more than likely, disappear at the first sniff of a 737 job.
Similar to others I have fairly strong views on self funded type ratings.