I say stay put. DH and I welcomed our first baby while living in a 399 sqft 1 bedroom apartment. It was a lovely little place, and we dealt with the size quite easily by not having so much stuff.
You have been looking at this the wrong way (IMO) in terms of thinking the condo was going to be a money maker for you. A house isn't an investment, it's a place to live. It sounds pretty sweet in terms of location. Our apartment was in a small town, and it was totally priceless that i could just strap the baby into a carrier, and walk into town for the library or whatnot. Carseats and driving a baby around is such a hassle.
Is your wife set on being a SAHM? Because I out-earn my husband by about 300%. I hated my job at the time our first arrived, so I quit and stayed home for a year. But for the 5+ following years, he's been the stay at home parent, except some part time work that coincided with maternity leave with our second kid, and recently taking some seasonal full time work. (kids are almost 7 and 4 now.)