All 4 could be broadened:

1 have rich parents (not kidding) >> Parents

2 work part time until you can get angel investment >> Another income

3 a pre-angel incubator ala YC >> Small investment/tor

4 live somewhere really cheap and use savings >> Savings

I think all 4 imply also living cheap

Yes, but it's not just living expenses -- I was thinking along the lines of can your parents float you $25K for startup costs such as equipment and working capital? How about $100K? Is it a big deal if they don't get it back, ie is this their retirement, or is just kind of a bummer? And so forth...

The startup I was thinking of needed the money in order to establish business relationships -- the business they are in requires quite a bit of working capital. The founder's parents basically gave him $150K and they aren't so rich that they wouldn't notice, but if he had lost the money, it wouldn't have been a particularly big deal. (Sorry, I'm not trying to play coy, so if anybody is interested, email me and I'm happy to give names, but I just don't want this account to be googleable.)

Edit since I can't reply and want to go to sleep -- yes, this makes your parents angels, but getting angel investment suffers from who you know -- how many people grow up knowing angels? So your parents offer three major advantages:

1 - you know them already

2 - you know them already

3 - they are probably more willing to take a chance on you... and you know them already

I think when you get into the "parents give you $150k" range, the parents in question fall more into the category of angel investors than anything else.