Mary Anne, did your contract/ your lease stipulate they were putting in a tub? I hate to tell you this but... if you moved in, saw there was not a tub, saw only the shower, and this was not brought up either written or verbally, then, Mary Anne, it is what it is.
If you plan on staying there, you could try mentioning it to them, but, I would not expect them to put it in. The bath is finished right? You cannot fill up that area with water you will have a huge mess loads of possible damage, if I am understanding correctly what you are saying you want to fill up and asking about a wobble. That is meant only for a shower and will not hold water like a tub.
I wish I could tell you some happier news Mary Anne. One thing, there are still lots of first-time home buyers incentives out there, and you maybe, could be looking into buying a home. Save up alittle and make that your dream! If you husband is a VA or you, you could use your VA benefits with a no down payment, and a much lower interest rate than what the market holds for a conventional.
Hope this helps, if it doesn't I hope someone else will chime in with some good advice.