As believers, we are not to see how close we can get to sin without falling but rather to flee from ungodliness.

2 Tim 2:22

Now flee from youthful lusts, and pursue righteousness, faith, love and peace, with those who call on the Lord from a pure heart.
NASB

Your neighbors assume that you're married by the picture your living together paints.

1 Corinthians 6:9-11
"Or do you not know that the unrighteous shall not inherit the kingdom of God? Do not be deceived; neither fornicators, nor idolaters, nor adulterers, nor effeminate, nor homosexuals, 10 nor thieves, nor the covetous, nor drunkards, nor revilers, nor swindlers, shall inherit the kingdom of God. 11 And such were some of you; but you were washed, but you were sanctified, but you were justified in the name of the Lord Jesus Christ, and in the Spirit of our God." 

A "fornicator" is someone who has sex outside of marriage.

Hebrews 13:4
"Let marriage be held in honor among all, and let the marriage bed be undefiled; for fornicators and adulterers God will judge."

Galatians 5:19-24
"Now the deeds of the flesh are evident, which are: immorality, impurity, sensuality, 20 idolatry, sorcery, enmities, strife, jealousy, outbursts of anger, disputes, dissensions, factions, 21 envying, drunkenness, carousing, and things like these, of which I forewarn you just as I have forewarned you that those who practice such things shall not inherit the kingdom of God. 22 But the fruit of the Spirit is love, joy, peace, patience, kindness, goodness, faithfulness, 23 gentleness, self-control; against such things there is no law. 24 Now those who belong to Christ Jesus have crucified the flesh with its passions and desires."
NAS

Ephesians 5:4-6  "and there must be no filthiness and silly talk, or coarse jesting, which are not fitting, but rather giving of thanks. 5 For this you know with certainty, that no immoral or impure person or covetous man, who is an idolater, has an inheritance in the kingdom of Christ and God."  NAS