Hi S., I agree you should WAIT to get another bedroom to avoid the financial strain. My only thought/concern is the baby crying at night .. waking your 18 mo old (well by that time older).. and/or your husband! Then you'll have 2 children awake to deal with & a tired husband (& yourself?) waking up for work the next day.(hint: earplugs work; share nights w/your husband!) Tho IF you take on the extra ($185) expense when you're NOT ready -- you & your husband may just have sleepless nights ANYway.. up worrying about finances!! :} I've been there!!
Once your children reach a certain age, & you're ready to move into a bigger place, you may still want to continue your children sharing a room. If you have SAME-sex children; consider bunkbeds. I believe there are specific sibling rules (laws?) if the children are OPPOSITE-sex,only once they reach a certain age.. but you have plenty of time for that.
My boyfriend & I (both grew up in '60's)shared rooms w/siblings. I actually slept in the same bed w/my sister(s) until I left home; actually there were 5 of us .. we couldn't wait for one to leave home so we'd have more room!
Recently, this topic came up in my family concerning my 7&9yr old (orphaned) neices who went to live w/my sister; they WATNED their own room tho it wasn't practical ..my sister allowed it anyway!
Even tho I had researched (google) for info/help & found websites/studies on the topic. One quoted a 'Tufts Child-Development Study' which read: "Now-a-days each child having their own room is typical in US households but NOT always necessary OR the best choice".
The 'child-development expert' went on to say: "over the last 30 yrs the size of the average home in US has swelled by nearly 1,000 sq ft.. giving families plenty of room to spread out", "BUT giving kids too much space has some tradeoffs & NOT the best choice".
'Tufts- Mr. George Scarlett' told the Washington Post "sharing a room can help kids w/their sense of attachment & security". "It teahces them (valuable lessons) to cohabitate efficiently, tidly & peacefully for the future" (off to college room-mate). Studies have shown a strong bond between siblings who share a room.
Financial Advice: Now-a-days there may be 'at home' (on line?) work projects you may want to consider taking on for extra cash--working at your own convenience. Tho I realize being 3 mos pregant w/a 18mo at home (& especially if you work TOO?) is NOT easy!
Well here is some more Website (google)info: www.parenting.com had an article which read: "benefits of siblings sharing a room offers plenty of real-life opportunity for kids to learn the art of negotiation & problem solving".... "Spooky nights will seem less scary"... "children learn to respect other peoples differences"...
The 'Tufts Child development Study' had also found: "siblings who share a room tend to be closer as adults". . They say "siblings 2 to 4 yrs apart CAN tend to be angry w/each other & bicker" & thus the need for privacy & space within the room.
Hope this helps... Good luck & God Bless..