New-build SFR in Austin metro: builder buydown to 5.15%, but 2.7% taxes and negative

First rental purchase. I've underwritten this to death and keep landing on "no," but the financing is unusually good and I want a sanity check from people who've actually done this in a Sunbelt market.

TL;DR — New-build 4 bed / 2 bath SFR in an Austin-metro exurb. Builder is at $272,999 with a 5.15% 30-yr fixed buydown (market investor rate is 7.3%+) plus a 2% closing credit. Great financing — but property taxes are 2.726% (there's a MUD in there), HOA is $119/mo, and 4-bed rents locally are $2,185 and falling 4% YoY. Assuming I pass the ~$70 internet portion through to the tenant, that shakes out to −$131/mo self-managed, −$299/mo with a property manager, a 4.24% cap rate and a 1.07 lender DSCR. My breakeven price is about $252K — a $21K gap to what they'll accept.

The question I'm stuck on: is a genuinely below-market, 30-year-fixed rate a good enough reason to buy at an above-market price? Or am I just paying the premium in a different envelope?

The property

• Market: Hutto, TX — Austin MSA exurb, Williamson County, ~25 min NE of downtown Austin
• Type: New construction SFR, 2026 completion, national production builder
• Specs: 4 bed / 2 full bath (no half), two-story, 1,897 sqft, 0.10 acre lot, 2-car garage
• Status: Still under construction, currently listed and unsold
• HOA: $119/mo — includes high-speed internet, pool, playground, sport court
• List history: listed $286,999 → cut to $276,999 → builder now offering $272,999

The deal on the table

Income and expenses

Rent estimate: $2,100/mo ($1.11/sqft). Local 4-bed average is $2,185 and down ~4% YoY. I'm discounting because this is a 4/2 — three bedrooms upstairs sharing one bath, owner's suite down — so it competes below the 4/3 and 4/2.5 stock.

Tenant's all-in housing cost is therefore $2,170/mo ($2,100 rent + $70 internet) — versus a local 4-bed average of $2,185. The logic is that the tenant would buy internet anyway, so bundling it is roughly cost-neutral to them. Tell me if that's wishful thinking.

The metrics

Breakeven purchase price for $0 cash flow: ~$252,000 self-managed, ~$226,000 with a manager. That's $21K–$47K below what the builder will accept. (If the internet pass-through doesn't hold, those drop to $242K / $216K.)

Two things that surprised me

Taxes are 2.726% effective. Base stack here (school + county + city + ESD) is ~2.095%, so there's roughly 0.63% of MUD or PID on top — about $1,720/yr. Taxes eat 30% of gross rent. The listing shows $1,474/yr because that's the land-only assessment on an unfinished house; the real bill is ~$7,442.

HOA is $119/mo, not the $60–70 I'd budgeted — it bundles high-speed internet. I'm modeling ~$70 of that as recovered from the tenant, so my net carry is ~$53/mo after adjusting for vacancy months when I eat the full fee. Sensitivity on how much actually sticks, self-managed:

Why I'm not counting on tax benefits

I'm underwriting this as if the tax shelter is worth zero in the early years. Passive activity loss limits apply in my situation, so rental losses suspend and carry forward rather than offsetting ordinary income, and there's no real estate professional status in the household.

Over a long hold the suspended losses do release at sale — but they get largely offset by depreciation recapture at 25%. Net of both, I treat the tax treatment as roughly neutral, not as a subsidy. Cost segregation plus bonus depreciation would throw off a large year-one number, but in my case it would just add to the suspended pile.

If your view is that I'm being too conservative here, I'd like to hear it — but I'd rather a deal stand on its own cash flow than lean on a shelter I can't currently use.

What's actually good here

• 5.15% fixed vs a 7.28%+ market investor rate — about $290/mo cheaper than market, equivalent to roughly $55K off the price in payment terms.
• Brand new: 1-2-10 warranty, low repair variance for several years.
• The builder ran ~12.9% incentives company-wide last quarter against a stated 4–6% "normal," so I believe I'm buying into real builder distress, not a fake discount.
• Price has moved $14,000 off original list and they're still negotiating.

What worries me

1. Rents are falling (−4% YoY) while any pro forma I write assumes growth.
2. The builder is still delivering homes on the same street — I compete with new inventory on rent and on eventual resale, and they can discount in ways I can't.
3. Build-to-rent operators may hold the same floorplan in the community. Haven't confirmed how many.
4. 4/2 configuration limits the tenant pool vs nearby 4/3 stock.
5. Retail price, zero instant equity, from a seller publicly cutting prices.
6. A 3.5–4.2% cap rate is barely above what T-bills pay, with none of the risk.

My questions

1. Does a ~4% cap with negative carry ever make sense if the financing is genuinely below market and fixed for 30 years? 
2. Or is "below-market rate on an above-market price" just the premium repackaged?
3. What reserve % do you actually use on new construction? 
4. I used 2% maintenance + 3% CapEx. Too light for a long hold? Should I phase it (near-zero years 1–3, ramping later) rather than use a flat rate?
5. Can you actually recover a bundled internet fee from a tenant? 
6. I'm assuming ~$70/mo of the HOA comes back to me, on the theory the tenant would buy internet anyway. Does that hold in practice, or do tenants just treat it as rent and push the total back down?
7. How do you underwrite MUD/PID risk? 
8. Does the rate reliably decline as district debt amortizes, or should I assume it holds? What should I ask about the service plan?
9. Am I wrong to discount the 4/2? 
10. How much rent penalty vs a 4/2.5 or 4/3 in a family-rental submarket?
11. Anyone bought new construction in an Austin-metro exurb in the last 18 months — how did rents and vacancy actually come in vs your pro forma?
12. Would you walk, or hold at ~$252K and let them say no?