Answer:
Edward had a childhood love Lucy who he had broken up for quite a few time and knowing the fact that she is going to marry Robert. On the contrary, Elinor had a past too which she had left far behind after falling in love with Edward.
They were so comfortable knowing each others past they it no longer affected their relationship and all they knew was they will be happy together.
Living together came up with all of its consequences, they both knew each others financial condition and were ahead of it. as this was something that they considered wont in any case have an impact on their romantic life, as long as they are together.