When will I get Eggs?

At 18 weeks, they don't need extra heat. A heat lamp in the coop is a fire hazard and if the power goes out on a very cold (single digits) day/night you may loose some birds to the cold, because they haven't had a chance to acclimate to it.
Pullets that mature in the fall can take longer to mature due to the shorter days. They may not start laying until the days begin to length, sometime in January.

 

Ditto...no heat...be patient.
18 weeks is the beginning of the typical 18-24 weeks that most breeds begin to lay.

You could check pelvic points....if you free range might want to keep them confined.



Signs of onset of lay---I've found the pelvic points to be the most accurate.
Squatting:
If you touch their back they will hunker down on the ground, then shake their tail feathers when they get back up.
This shows they are sexually mature and egg laying is close at hand.

Combs and Wattles:
Plump, shiny red - usually means laying.
Shriveled, dryish looking and pale - usually means not laying.
Tho I have found that the combs and wattles can look full and red one minute then pale back out the next due to exertion or excitement, can drive ya nuts when waiting for a pullet to lay!

2 bony points(pelvic bones) on either side of vent:
Less than 2 fingertip widths apart usually means not laying.
More than 2 fingertip widths apart usually means laying.