Your trim design is easily made onsite. Because you want flat trim rather than trim with a curved profile, you won't need to do coped joints. HERE is a picture showing common base trim. Remember to only rout the top outside edge of your trim; you don't want a gap against the wall or floor, etc.

You definitely want to bring your trim boards inside your home for two weeks before you begin to cut and fit so the wood has time to expand/contract. Otherwise the wood may contract and leave a gap, or expand and bow. The same is true for any wood flooring. Give it time to adjust to the internal humidity of your home.

> I am planning to have stained wood trim

You need stainable material. Poplar doesnt count in that category. I would not use soft pine either and if you paint these big nots will bleed some sap for years to come.

> I was disappointed with the selection of trims available in Home Depot and surprised at the price.

If you are " surprised at the price" at home depot - you may be more surprised at the price at the lumber yards.

> have any of you made your own baseboard and window trims?

Countless times. These trims are really easy and may not even require a router. But if you use one you will probably burn the edges... Before applying heavy/wide trim check all doors, esp kitchen [pantry, cabinets]. Some doors may be like 2" from the wall or kitchen cabinets leave 2" for trim. It will look funky having 6" trim / 8" block on one side and 2" trim on another.

Good luck.

The lumber to make a quailty stain grade trim will not be inexpensive. I would do exactly as Jeffrey ^^^^^ suggests above.

You can sometimes get deals on craigslist for hardwood, new or used, either rough-sawn or surfaced. We have sawmills in our area that sell native hardwoods, usually rough-sawn for more reasonable prices, mostly air-dried but some kiln dried. More of an investment in tools and time though. I am using wood I removed from a porch floor for all of my trim on my current project.

Don't do it. Postpone the house and save up the money to pay for the trim if you have to/can or take out a bigger mortgage. The LAST thing you're gonna want to worry about it trying to make trim at the end stages of building the house. Are you planning on installing the trim yourself?

rayslady, what wood species are you planning to mill for stain-grade interior trim?

If you need to purchase clear, planed material or if you value your time at more than $1/hr, I think you'll find it more economical to purchase your interior trim from a millwork supplier.