A raft pretty much is a floating cart, for all intents and purposes. It's a fairly small transport vehicle that isn't capable of independent propulsion. On a more practical note, the only notable body of water you're liable to be in contact with is already well-traveled enough for transport to be cheap.
Non-Druid/Ranger animal companion/arcane caster familiar animals are, like many other things, part of your WBL insofar as that they are material assets (as opposed to personal keepsakes/plot hooks). You might be able to acquire fertile eggs of various species from time to time, but anything more exotic than foodstock is going to be costly -- Phynxkin, for example, are pack hunters which conceal their nests and tend to hunt travelers naturally, not to mention that even trying to find them would entail going fairly deep into the forest; most people wouldn't risk that for actual treasure, much less eggs of untamed animals.
That said, I can probably do a rough extrapolation from the cost of a Psuedodragon egg, which according to MM text is apparently listed at 10k gp. So maybe 250gp for a fertile Monitor Lizard egg, considering that it's a nonmagical animal but still a significant threat to the average joe trying to get some eggs to sell. More for a Phynxkin egg because of the reasons listed above. Something like a common, non-venomous snake/lizard egg would be cheaper, and a fowl egg markedly cheaper than that.
All other things aside, think long and hard about whether you want to invest money in something which requires you to spend long stretches of time in civilization doing a job before it shows appreciable results -- if it ever does.