Hi Everyone!

First time poster here, but LONG time MMM follower. Hmm, where to start on this....

The wife and I have been looking at moving for the last couple years. Never could really find what we want in a house without a large remodel so we decided to build and are in the process of such. "In process" as in we decided on a builder and are starting the design of the new home layout. We arent planning on breaking ground until April/May 2019 so we havent really committed to anything else besides time. We've been in our current (and first) home for 10 years now and while the location is very ideal, theres a few irks with the home we have - low basement ceilings (6'8"), 1.5 baths with two kids (7 and 5yo), the house is coming up on needing new windows, roof, etc, etc as its just that time for the house.

Anyways, I keep flip flopping on whether Id like to move or not so Im being very thorough on all the numbers. Im more wishy washy than she is and she's the frugal one. ;) The current location is what keeps swaying us to stay. We currently save approx 75-80%++ of our income. "++" meaning that my comp plan is 75% salary and 25% commission and Im only factoring in the base salary on that savings rate. The only other debt we have besides the current mortgage is a new to me car loan which with my mileage reimbursements it evens out in my favor plus some extra. We have already purchased the new 1.5 acre lot with cash a few months ago. ;) Current lot is 2.7 acres, just for perspective.

So what Im trying to do here is calculate the cost difference of building a new home vs staying here and just paying off the whole deal and keep some of the other subjective stuff out of this exercise. Im pretty good with math, and ran through the numbers real quick but Im not sure of their accuracy. Complicating this a bit more, Im trying to calculate this based off estimated amounts for next year. Ok, so heres what we have going on:

**Current mortgage:**

$119k remaining at 2.875% - about 9.5 years left. Im calculating by May next year itll be around $108k remaining on the current mortgage

Current principal + interest payment is $1201.

**New Home:**

We set a budget of $450k for the house.

As mentioned before, we already purchased the land (not included in above budge number). $30k - for 1.5 acres.

We'll have $100k+ of cash to put forth for a down payment

Plus estimated $100-120k from the sale of our current home

We'll probably hang on to a bit of that so lets say the new loan amount will be $275k after down payments - $100k from the house and $75k cash.

At 4.5% interest on a 30 yr note for $275k, P+I would be $1400ish, but we plan on adding on an extra $500 per payment so lets go with $1900 / month - essentially making this a 17yr loan. Technically, we could do a 15 year loan, but I like the idea of putting a set extra amount per month as we desire rather than committing to a shorter loan for a few points.

So reading through the sitch, you can see that we can outright payoff our house next year if we want to, and be done with any type of debt. Totally 100%. FU money would accumulate fast. In doing so, we'd save $13k in interest, sell the land. So we'd be "up" +$43k. Plus, I guess i need to factor in all the money saved by not building a new home to make it apples to apples?? I feel like Im missing something here though....

Now, if we build we'll be looking at the cash down payment ($75k) + loan amount ($275k) + load interest ($226k) and now that I think about, therell be interest only payments for the construction loan, during the construction period, before its rolled into a mortgage...lets say $5k total for that. Grand total: -$581k.

Im sure Im missing stuff here. Does this make sense what Im trying to calculate? Can the mustachians help me out with the numbers on this?